Recently had the experience of an impatient driver running a red light behind me, then pushing me and angrily waving at me in the rear mirror to speed up. When their was a two lane part he rushed past me. But the next few kms were trafficlight heavy area's all two lane, but no matter what he did, he never got much more than a few 100 meters in front of me. His angry-stressed- and frankly very dangerous driving got him to his destination 5 seconds earlier on a 15 minute trip than me, just patiently flowing with traffic. I tend to believe, these people are in a rush to the end of their lives, but sadly also that of others.
I finally found an urban planning/transportation youtube channel that doesn't just make 50 videos on "car bad" with points that everyone else has covered already, and instead provides actual new content
Coast to a stop is great for fuel economy (on non-electric/hybrid cars), but accelerating slowly to save fuel was mostly a thing on old carburetor engine cars (I.E. approx 40+ year old cars) as they weren't as good at having the optimal fuel-air mixture, especially during acceleration. (Technically a "gasoline engine" (really "Otto engine") is the most effictive at the point where you reach max power at a given RPM. I.E. pedal almost to the floor at the highest possible gear. There are a lot of caveats though, like for example cam/valve timing and whatnot, and modern (as in the last 20 years or so) cars have variable valve timing which complicates things). Drivers ed in for example Sweden teach to accelerate swiftly and when accelerating fast enough skip gears. (Drivers ed is almost always done for manual transmissions). The reason is that this is actually more efficient.
@@Thesecret101-te1lm Doubtful. My own fuel economy shows as much when I accelerate gently in my 2019 Nissan Sentra. If I gun the engine to get it to the speed limit, the fuel economy is less than 7 mpg. If I barely touch the accelerator pedal, I can get it to 20 mpg. I don't do it on busy roads.
@@ddrhazy i think the idea is u are in the less efficient acceleration portion. U spend slightly more time at consistent really efficient speed. Idk tho would need testing
It is not high speeds that leads to signals. It is the increase in access points and traffic generators that require changes in assignment of right of way.
@ I agree that number of crossings with streets is main factor, what I meant permission for higher speed limits causes even more hardships for drivers to turn into such stroad, so usually, the most primitive solution to this problem is implemented- traffic lights. The real deal is a proper division of traffic into roads and streets like in the Netherlands
@@paweuutrzrzrz2699 Speed only matters when the road is not at full volume. If the road is at full volume, then it doesn't matter how fast the traffic is going. Perpendicular drivers can't cross or enter. Controlled junctions are added when roads are at full enough volume that this state occurs enough to be disruptive.
@@Descriptor413 Designed so well that bus drivers can snap and change lights? (I'm sure its just transit signal priority, but I thought it was funny how he snapped like that)
It is sensor based, but sometimes even high priority has to slow down for a second. I play this game in the late hours on my bicycle. Pure fun, only one light forces me to a full stop every time. Think I am going to write a big complaint to the municipality...
@@Sullyville It may seem like magic, but it's actually due to the efficient traffic management system. Especially at night, when you approach an empty intersection, the traffic light turns green just before you arrive. That's why I love driving in the Netherlands.
You should repeat the Douglas boulevard scenario but the driver incrementally decreases their max speed for each trial. Make a plot of average speed vs max speed to visualize the non-linearity.
you will get very few converts here in the US. A lifetime of being told that we are special and individualistic has taught most people that while driving they are an island in competition with everyone else on the road who is just in their way and that the goal is to always get in front of as many drivers as you can no matter where you are. Oh, at it has told us that it is cool to drive super loud cars very fast around other peoples neighborhoods in the middle of the night. Go USA #1!
Filming your daschcam footage from inside of a bus? You are an urbanist, my friend. (Just discovered there is no bus emoji. Work of the "car conspiracy?")
Driving aggressively >might< get you to your destination 'sooner', but the amount of energy expanded is exponentially higher and the recuperation time afterwards will be a net loss relative to any travel time gain. I wonder if there's any scientific studies into this phenomenon.
In the Netherlands because the vast majority of traffic lights are sensor based, aggressive driving in some places can net you a time benefit. Also, because you may be able to squeeze yourself into an earlier traffic light cycle. But this varies a lot depending on the location, traffic volume, and configuration of the lights and such. It's also just plain wasteful.
Hi Celis C, what are trying to do is pure science!, all your need is careful critical oversight of the information you use for your calculations and sensible reliable observations, do your best to exclude subjective assumptions and then allow your brain to think to all through, at some point it will offer the outline of an explanation that correlates with your observations. the next part is to formulate what you come up with into a useable hypothesis which you can then test, the easier it is to test and thus refute the better it is!. All you require for total refutation is just one bit of empirical evidence that confounds the hypothesis which you then abandon and wait for a new one, each time you go through this process you learn another thing that is not true, a properly proven fact, this way you increase your total body of knowledge. In this particular context we can start with a number of scientific principles which we accept as established, these include the given assumptions that the greater the speed of the traffic the more vehicles pass any given point at any given time the greater the total traffic flow, one reason for this is that while the lenght of each vehicle does not vary with speed the distance between them does, in fact with any given number of vehicles of any specific length there is a minimum threshold below which there is no space between them at all at everything stops, it then takes a finite amount of time for them all to start moving again further reduce the flow rate. From all this it follows that fewer shorter vehicles all travelling at a constant speed with the same minimum space between them would be optimal, that however is the 'perfect' state scenario which for very good reason can never happen because reality includes variation and diversity, these factors are much more difficult to enumerate but that is not needed!, allm tht is needed is effective traffic control that reads the flow rate and as it drops reduce the vehiclers allowed on that road, when the flow rate rises again near to the proximate optimal threshold more vehicles can be allowed to join. From that in situations where the backlog at the access ramps become too much other measures must be applied, there is an obvious range of options all the way from reducing the size of vehicles to adding more lanes and building new roads or as a last resort providing adequate public transport using its own part of the road network so that travellers sitting waiting in a car for a space on the road will see bus after bus not full of passengers passing them and they can make their own choices. The manner in which each of us choose to drive has little or no material effect on the whole traffic pattern, it might be 'true' that if all drivers applied exactly the same style we could get more traffic on the same roads but they don't and they won't all do the same as each other. Regardless of political ideology we should be just rational and practical. Cheers, Richard.
@@wewillrockyou1986 I don't think he just means fuel energy. Aggressive driving makes you angry and frustrated, which costs so much more mental and emotional energy for only a minute gain on a 30 minute trip. I always laugh at cars on the high way, push me to the side, speeding up only to be stuck behind the next car they have to push again. In the end they exit the high way only a minute before me, but are a thousand times more frustrated....
Ive often wondered about this, figuring that increased speed must improve capacity, but get balanced out by greater following distance. It was really nice to see you sit down and go through the numbers. Subscribed!
→ 3:38 Please use a better multiplication sign - at least one which is centerer. A centered dot (·) works, or even a centered diagonal cross (×). But this six-pointed raised asterisk (maybe a font variant of *?) is definitively not a multiplication signs (at least use the centered one (∗), if you must). - 5:27 Somehow you here managed to arrange the asterisks with the center line here? → Another part to consider is whether the 2 seconds of following distance is actually safe enough with higher speeds. I think you'll actually need more distance to be able to safely stop in case of an accident in front of you.
Love you point about not being an "urbanist" and the service your channel provides. It wasn't long after I discovered NJB that I thought, "ok, cars are bad, but I want to actually argue with engineers about why things need to change in the US." I wanted to know the actual math. Thanks for providing this side of the narrative. I think you're one of the few RUclipsrs doing it.
Putting engineers in charge of decisions that are political decisions not engineering decisions is part of America's problem you shouldn't have to argue with an engineer about this the engineers should be told what to build and their job is to figure out how.
@@supermanifolds You can't order someone to beat physics. So no, engineers need to have a say in things. And by the way...how do we determine what our orders to engineers look like? Mind you, it is not a theoretical question. In Canada, we see exactly that kind of thing being played out right now. A politician, probably with reasonable backing by his voters, orders bike lanes to be removed.
@@supermanifolds Whereas I think these decisions should be made by engineers, not politicians. Maybe politicians can set general goals, but as they usually do not understand how these things work, they should be as far from the actual decisions as possible.
In the UK, the Highway Code requires driver to drive within their stopping distance which is a quadratic relationship to speed due to Kinetic Energy being proportional to the square of velocity. In you model you used a linear relationship. If you had used the quadratic relationship you would got the answer that slower speeds always increase capacity. You can see that in action in reverse: when traffic increases speed naturally decreases (congestion) to accommodate the need to increase traffic capacity.
A moving car does not suddenly stop from one moment to another. It is bound by inertia and will slowly come to a stop in a reasonably similar way to the following car. Your distance only needs to account for your own reaction time, so 2s is reasonable. And at least here in Germany it is explicitly coded into law. Probably in the Netherlands as well. Looking at existing traffic out in the world, 2s seems like a gross overestimation. At highway speeds this should turn out to around 60m, but I often find traffic on the left lane too bunched up to even attempt fitting a 5m long car into the gaps ;)
Except in motorway conditions this is tricky. The 2 seconds rule is to account for delays due to reaction speed, but also taking into account that the car in front is not stationary and has its own stopping distance. In reality it would already be great if people kept the 2 second distance on the motorway. For urban traffic the stopping distance is more important, but when adding reaction speed 2 seconds is a good rule of thumb for normal conditions.
Kinetic energy going up by the square of speed is not the reason why stopping distance goes up by the square of your starting speed. That correlation is a myth! Stopping distance can be calculated by multiplying the time it takes to stop, by the average speed. And increasing the starting speed increases both the time _and_ average speed. For example, lets assume we have a car that can brake at a constant rate of 5 m/s/s. If we start at 10 m/s, then it would take 2 seconds to come to a stop, and our average speed would be 5 m/s. So our stopping distance would be 2s * 5m/s = 10 m. If we start at twice that, 20 m/s, then it would take twice the time (4 seconds) and our average speed would also be doubled (10 m/s). So we get 4s * 10m/s = 40 m. If you want a visual, then we can plot this on a graph with speed on the vertical axis, and time on the horizontal. With a constant rate of deceleration like in the examples I gave, then we'd get a straight line with a downwards slope. And the area would be triangle shaped, hence why the average speed is just half the starting speed. (And I'm ignoring drag and the slight lift most cars get from being airfoil shaped. As they roughly cancel out.) And _most_ land vehicles generally have close to constant deceleration when braking. As the resistance from friction (both in the brakes and tires traction) goes up with speed at the same rate as kenetic energy does. And perfectly cancels it out, making the exponential nature of kenetic energy a non-factor in stopping distance.
@@PauldeVrieze The car in front might not instantly stop but another car might pull into your lane or a pedestrian might step out. Either way Rule 126 says "You should leave enough space between you and the vehicle in front so that you can pull up safely if it suddenly slows down or stops. The safe rule is never to get closer than the overall stopping distance (see Typical Stopping Distances diagram)". The stopping distances in the diagram show reaction distances increase linearly with speed but the braking distances increase by the square of speed.
@@vulduv The official braking distances in the UK go up according to a square law and it is those distances together with a linear thinking distance that UK drivers are required to leave between them and the car in front. At 32 km/h the thinking distance is 6m and the braking distance is 6m giving an overall stopping distance of 12m. At 64 km/h the thinking distance is 12m and the braking distance is 24m giving an overall stopping distance of 36m. Whatever you might think, these are the gaps that UK drivers are required to leave.
It’s great to explain these mobility concepts. Would be good to also explain how travel time is only marginally reduced as speed increases (between fixed points). And energy increases exponentially…
Suggestion for future topic: What are the actual effects of "green wave" traffic lights? I.E. ensuring that a bunch of traffic lights along a major roads are green at each junction for traffic that isn't turning? Also re 1+1 roads (without overtaking abilities) v.s. 2+2 roads: I would say that it's not just about aggressive driving and whatnot. It's also about calm driving. It at least feels way less aggressive to set the cruise control to the legal speed limit (where that is actually reasonable) and overtake everyone who thinks their speedometer is showing actual speed, and thus drives 26km/h on a 30km/h road. Modern cars have automatic distance adaption for their cruise controls, but older cars don't, while at the same time even older cars tend to otherwise have excellent cruise control (kind of thanks to drive-by-wire being the norm for the last 25 years or so). Driving without cruise control also takes away attention from traffic as you every now and then need to check your speedometer. Also re 1+1 vs 2+2 roads: At least in Europe it's fully legal (and I think this is great) for vehicles to be "underpowered", as in a car with say 100-120hp are allowed to haul a total of 3.5t (car + trailer), and those will obviously accelerate slowly, and in that situation 2+2 is great. Sure, a rare case, but not unheard of.
You are assuming people won't just fill both lanes and travel at the same speed. It happens here all the time. I've been on a 3 lane road trapped behind 3 cars all doing about 15 under the limit, all in their own lane.
SOme 30 years ago such a system was installed on a road in Southampton. Whilst on a course in the centre of town I car shared with someone who knew all the short cuts around the traffic queues. We shot right at junctions , sswung left at others, raced down side streets , stopped at traffic lights and got to the destination. I was timeng the drive unknown to the driver. The next day it was my turn, I followed the green wave on the main road, at the moderate speed allowed, with few gear changes needed and little braking. We arrived 5 minutes quicker than the day before.
Max Traffic Flow: *Is 1800 cars/hr* Tailgaters in giant pickups: "That won't stop me. I didn't read the driver's manual." Jokes aside, how do traffic engineers compensate for areas where the majority of drivers are aggressive drivers that won't hesitate to break the law? Where I live 5-20 mph over the speed limit is normal (it actually becomes dangerous at times to try to do the speed limit), weaving between lanes is increasingly common, hogging intersections is common, and the general attitude is "the police can't stop us all".
Simple, make the roads more hostile to driving (and reduce hostility in areas where people drive nicely) Just like how you train a dog (cuz that's how these people behave. You drive fast: you loose a bumper You drive slow: one less speedbump for you. (there are lot more things you can do that speed bumps of course, like narrower roads, less smooth paving, more turns, on road obstacles, traffic lights, speed cameras, roundabouts etc.) Road width is the most common thing designed wrong in areas where speeding is too high. The narrower the road the faster you feel you're driving. So if the road feels like a 60mph road but the sign says 40mph, people are going to drive 60 even though those that don't necessarily want to break the law on purpose.
@@DrTheRich Speed bumps don't really encourage slow driving away from the speed bump though. They barely encourage slow driving on the speed bump these days. They kinda worked back when most people drove cars with very little power, but nowdays most cars can do 0-100 kmh in under 8 seconds, and any speed bump that'll break the spine of anyone in a hatchback doing 30 will barely be noticed by someone in an over-sized SUV doing 40. They incentivise buying more dangerous vehicles. Now lane narrowing, chicanes, roadside clutter (tall roadside clutter so SUVs will notice it) are probably better tools. Speaking of SUVs really make everything around you seem further away. I find it much harder to judge my speed in them - though I haven't driven that many. Maybe we should just ban them all together and fix that problem.
Very interesting video! One factor beyond traffic flow to keep in mind though is the time saved by individual road users when they get to go faster. Time-efficient travel drives economic growth, which is why humans have always strived to find faster ways to travel: railroads, highways, freeways, airplanes, bullet trains, ... Of course, there is a balance to be found where accidents on ill-adapted infrastructure will also negate these economic gains after a certain point. Furthermore this applies more to long distance travel rather than core-urban travel, but it still matters
The engineers know that theoretically, speed for freeways has no impact on maximum capacity. However, at higher speeds, this reduces the average amount of time one vehicle spends IN the system, meaning that the system will clear up sooner for OTHER drivers to use it. For example, if the free flow speed on a freeway was 20mph instead of 80mph, that means on average, each vehicle is spending 4 times longer in the system, meaning any additional vehicles that want to enter the system have to wait 4 times as long to get a "spot". While not affecting freeway capacity in the literal sense, it is easy to see how increasing the average speed on the system improves things. It's all about clearing the system as soon as possible for other vehicles to go and use that capacity, which is something transportation engineers must also take into account. The lack of effect on freeway capacity is a result of how capacity is defined, not evidence that increasing speed is useless and counterintuitive. There are real benefits, even though there is also a real cost (increased fatality rates). The same can be made for the argument against adding lanes to freeways or roads. Engineers also understand that adding more lanes will not usually lead to any long term benefits in travel time, but it does (up to a point) improve highway capacity, meaning that even though it will still take you 20 minutes to go from point A to point B, regardless of whether the road has 3 or 4 lanes, the road with 4 lanes will be able to carry more vehicles per hour at that speed, whereas before, with only 3 lanes, it was unable to carry that capacity which led to a reduction in highway level of service. And obviously, if you've ever driven on a road that has more than about 4 lanes in one direction, you realize experientially the inefficiencies that arise that result in diminishing returns from adding additional lanes, especially in a high ramp density segment of the freeway. It turns into chaos, and is more dangerous, and at some point, the massive costs outweigh the additional capacity of another lane. Because of all of these things, adding a 16th lane is a lot less useful and more expensive in the long run than adding a 3rd lane. As for your stop and go traffic analysis, I have nothing to say because I think you explained it better than I could. And I also don't like our reliance on motor vehicles, and I think major metropolitan cities like Atlanta and Houston are enough evidence that designing primarily for cars is a bad idea. However, it IS more complicated than that, and youtubers like "Not Just Bikes" don't seem to understand this. Many cities now are simply too low density to use anything but cars or rapid transit, but public transportation is awful here in America. In my opinion, the way to go forward for American cities is to start making downtowns inaccessible to cars, and cordon off downtowns into pedestrian and emergency / commercial vehicles only. Reduce the size of these vehicles to their european counterparts that still function well enough, and then you can start narrowing roads and getting rid of all of that asphalt. You can add some green space and even have some street markets in the middles of these roads, and building pedestrian friendly spaces. You can have multi-story parking garages on the outside of this area and make use of the 3rd dimension instead of these horribly large and inefficient parking lots. Eventually, as funds allow, these buildings can be expanded into the street, or courtyards can be added. You can have public transit going to downtown, and creating more of these car-inaccessible spaces and treating cars more as transportation between two areas instead of as a mobile base will be helpful. Not everywhere in a city needs to be accessible for cars.
In the meantime the suburbs could also be made more liveable by allowing local shops and restaurants to operate there. More people will use sidewalks if there are destinations where people actually want to walk to. And if more people walk, more people will ask for additional sidewalks (and bicycle paths). I live in a quarter of a (Dutch) city that was built in the 60s. When this country was still firmly on a car-dependent path. They built high rise apartment buildings, family homes and schools and planted some trees, but hardly any shops. These were retrofitted much later. Nowadays everyone in this quarter lives within walking distance of a cluster of 3-4 shops (bakery, vegetables, butcher, convenience shop, café/restaurant, drycleaner and/or a small supermarket). And there is a larger shopping mall with larger supermarkets, clothing shops, book store, drugstore etc. in the middle of the city quarter. From my home it's a 2 minute walk to the closest supermarket and butcher, 4 minutes to a bakery and snackbar and a 5 minute bicycle ride to the shopping mall. Because the shops are so close by, people can stay in their homes longer. My neighbour is 86 and can't drive a car anymore, but she can still do her shopping with her walker. Of course we help her when she needs something from the large mall or when the streets are icy (and too slippery for her), but I think it's nice that she can stay in the house she's lived in since in for the past 60 years, without losing her independence.
Your math makes zero sense. "the average amount of time one vehicle spends IN the system" means literally the same as "cars per minute" aka the same formula applies as in the video. you just describe it it a more convoluted and wordy way to be able to arrive at an incorrect conclusion
I have often checked the average speed record for my car. Over nearly 1000 miles I seem to average 36mph, in spite of most of my journies being at motorway speeds. I once left the Warwick services on the M40 to travel to Portsmouth. My employer left at the same time. He always drive at an indicated 80 mph, I never drove more than indicated 70, on motorways and dual carriageways. When we reached the destination , about 140 miles, my employer was just getting out of his car as I pulled up behind him. He had needed to wait at one set of traffic lights whilst I had not.
The use of * instead of either · or × is kinda driving me nuts. * is the symbol for the convolution, after all. Is the assumption of constant following time with speed empirically derived?
Assuming a linear increase of following distance with speed is wrong if you assume everyone drives safely. In Germany we learn to keep a distance that is greater than reaction distance plus breaking distance. Reaction distance increases linear with speed, breaking distance quadraticly. We learn the following approximation for the distance you should keep: (speed / 10 km/h)^2 meters If you use this approximation, there must be an optimal speed where the capacity is at a maximum before the quadratic exceeds the benefit due to vehicle length and additional speed reduces the capacity again. Edit: According to my calculations, the optimal speed is about 22.36 km/h with a road capacity of about 2236 per h. (The exact optimal speed is (square root of 500) km/h. The 500 comes from the 5m vehicle length and the square of the 10 from the approximation for breaking distance.)
You can do the calculation without having to need the approximation. You do need to chose a braking decelaration though. Assuming 5m/s² (and car length 5m), the ideal speed becomes 7m/s (= 25,2 km/h) with a max theoretical throughput of 2230 cars/hour 30km/h => 2204/hour 50km/h => 1847/hour 70km/h => 1499/hour Very similar results. Also interesting: if self driving cars don't need reaction time (because they communicate in advance). The capacity for a 50km/h speed would increase to 2058 cars/hour (increase of around 11%)
The formula F = s*d*t is misleading. The units don't match up (s is in distance/time, d is distance, t is time/time (seconds per hour)) which multiplies to distance^2/time, where you actually want 1/time (rate of cars per unit time). But when you do the formula example, you express following distance as "1 car per 27.8m", which is actually _dividing_ by following distance, not multiplying. So it should be s*t/d. If this is some traffic engineering formula, then maybe this discipline should get better with tracking units. Because it seems like you're treating the quantity "following distance" as an _inverse distance_ (units 1/m) rather than a distance, which is just confusing. Also, having "t" as a unitless quantity (time / time) is also deceptive. Why not just say that the car capacity rate is F = s / d, which gives you units of (time)^-1, and then just adjust the units accordingly. So if you have s in m/s, and d in m, then you get cars/second, and then just multiply by 3600 to get cars/hour.
(smart) roundabouts, over/under passes, merging lanes, rerouting traffic in smarter ways, reducing need for cars, lower speeds. If you play any city planner game, you'd realize that hard time-regulated traffic lights are amongst the worst naive solutions to solve a car crossing.
Nice video. You said that the Dutch have two different manuals; one for urban, and one for rural. What are the names of the manuals, if you don't mind?
Good video. Mythbusters did an episode comparing agressive lane switching to flowing with traffic on a highway if you are looking for more visual examples.
Idea for a next video: ideal distance between bus stops on a straight line for 30, 50 and 70km/h compared to population density. (you may assume an infinite amount of buses and passengers and their destinations are distributed evenly) Walking speed = 1m/s deceleration and acceleration = 3m/s² (or if you can find a more accurate number you can use that)
Regarding the following distance/time given at 3:56, how would self driving cars affect the variable? How much could self driving cars feasibly reduce the distance under 2 seconds?
2 seconds is the best case scenario WITH self driving cars. Self driving cars can reduce things like distracted driving when a car waits a second or 2 longer than it should to drive out of a cue. Or to get a bit closer. But theres still a minimum following distance so a car has time to stop if the car in front of it gets a crash and comes to a full stop. If you want to be more efficient, you might as well get out of the car and onto a bus since thats the only way you can start fitting more people in per square meter/foot.
@@buildthelanes Re having margins to stop if the car in front ends up in a crash - this might be the spiciest take ever, but given that cars have a theoretical capacity of about 4-6 people, while a bus can have 10x as many passengers, and thus it's reasonable for approximately 10 cars to crash into each other if a crash would happen, as it affects about as many people. In practice things like outcome of accidents and whatnot has to be considered. But the thought provocation is that it's more disruptive if a single bus ends up in a crash than if 5 cars crashes. In particular at low enough speeds, i.e. at 30km/h, it might be reasonable to actually have drivers drive close enough that pile-up crashes are unavoidable. (At low enough speeds there aren't even any noticeable damages if cars crash into each other. Can't remember the details but IIRC US regulations require this for 5mph, and it seems like this has been adopted world wide. In other words, at 5mph it would actually be reasonable to require drivers to drive onto the bumper of the car in front, to maximize capacity). Also re self driving cars: A major missing part about self driving is "hive mind". If there were provisions specific for self driving cars in the telecom mobile phone systems, to let them have a "hive mind", it would be super easy to have long stretches of cars slow down if an accident/incident happens. The self driving cars could also have a display turning on stating "slow - accident ahead" warning drivers of non-self driving cars. Another "hive mind" feature would be parking. If every car on a street in a city is self driving with a "hive mind", they could park in each other and just stop in the middle of the street, until a car needs to move, and then those who are in the way would just drive around the block like lemmings. Given that electric cars use very little energy when driving really slow this actually seems like a good way to increase parking space efficiency in cities.
This is a great question, I wasn't thinking it myself but I wish I had been. Thanks for answering, Stephan! Greetings from a fellow Dutch American Stephen.
I do wish the "distance" was presented as an inverse of distance in the a a beginning. I had to go back to figure out what you were talking about. It's strange that you call the amount of cars per unit distance "distance". Thanks for the otherwise clear and concise video.
Retail bicycle outlets need to do more to encourage young people and older adults to ride bicycles. Sponsoring bike trains to escort children on their rides to school would be a great start. Organizing volunteers, teachers and other to ride along would be a great start. Getting children out of minivans and onto bicycles would be healthy exercise, build independence and make society healthier. Fun ride should also be organized. Getting a local bike club or school to sponsor an annual event to a local park or trail would encourage both adults and children to ride bicycles. Getting local elected officials to help with sponsored activities would help to educate them about the need for safe, protected bike lanes and trails in their community. Offering space and coffee for local riders to meet up would also improve store traffic.
I would not let my kid ride a bike in the city, or most american towns. Its simply too dangerous. Pedestrians and Bicycles are among the fast growing fatality rates in the entire transportation system. Rides are great, but the city has to make actual efforts to develop cyclist protection before people would feel safe doing so.
@@cadenorris4009 That is why safe, separated bike lanes and trails are needed. It is so older adults and children can ride bicycles safely separated from cars.
I worked for a construction company in The Netherlands and they bought a plot of land in France to build a holiday bungalow park, outside town. The entrance of the park is at a departmental road where you can drive about 90km an hour, not an ideal road for cycling. And certainly not one I wanna risk my life cycling on. In order to sell the bungalows to Dutch people they asked the municipality to provide a separate cycle path from the park to town. It took almost 2 years to get the cycle path, because it isn’t (or wasn’t) common practice to provide separate roads for cyclists in France. But they wanted to accommodate the bungalow owners because they could revive a dismal local economy. It is great to be able to cycle 20min to the local bakery to get fresh bread every morning instead of getting it by car. A great daily exercise. It’s sad that there no other cycling paths in the area. It would be great to cycle around the area instead of sightseeing by car.
It is an inverse relationship. More density decreases speeds, less density increases speeds. Optimal capacity is a calculated balance between volume and speed.
Capacity constraints not typically faced by bicyclists. Here’s a consideration. Optimal conditions for maximum throughput. I’m talking professionals racing on a closed course. A 33-car Indycar pack at The Brickyard can probably fly by, all bunched together on the opening lap in… I dunno, 10 seconds? Meanwhile, the 176 members of a Tour de France day 1 peloton during the leadup to a sprint finish can go by in a similar amount of time. That’s more than 5x the amount of cyclists, and at the Tour, this is usually on public roads maybe half the width of the Indianapolis Motor Speedway. Obviously real world conditions do not reflect race conditions. Nevertheless, the difference is striking.
Wait. For the freeflow thing, the time between cars (even if we asume them to be dots) its not the same for every speed. Higher speeds typically mean less time between cars (it doesnt increase lineraly with speed)
A question related to the video (and not to the point you’re making): Why were you driving a bus on the 455 (and 32(?)) bus lines? Did Haarlem not trust you to drive a bus closer to home/work/in own province 😋?
I would expect higher speeds reduce capacity at some point because psychologically people would end up keeping longer distances to the preceding vehicle at higher speeds. My basis for this is observing driving on the autobahn, on average people seem to keep better to the 2 second rule at speeds of over 150 or so.
that's why he said 2 seconds and not 2 meters... That way it includes the longer distance at higher speeds. And an average of 2 seconds foor 100+ speeds seem fair too, because too many people sadly (including me admittedly) drive closer than that even, especially at a busy time.
My burning curiosity is this: can "smart", "networked", or "AI" intersections improve throughput significantly? My second burning curiosity is do lane jumpers increase decrease or not affect traffic throughput. Thanks for your answer, kkbye.
*FEEDBACK* Yes, the video does help. It's not an interest of mine, but it does help me a bit to become more knowledgeable. I don't think that it's too useful, though. *TOPIC REQUEST* I recall a guy sharing his discovery that slow driving in the right lane unplugs traffic jams much more quickly, as opposed to fast driving in either lane. It was so counter intuitive, but he somehow explained it. If you know that this is true, then would you explain it, please? Perhaps it incentivizes fast people to stay on the left.
Holding 2 seconds distance while going 70 - 90 km/h is nuts. And when all cars in a long row hold 2 seconds distance, it is a catastrophy waiting to happen. The formula for kinetic energy EK=0.5mvv is the key, here. Speed has the squared impact on it.
It's not nuts, is a common thought practice in driving schools across the world for highway driving. The thing you are forgetting in your thinking here, is that you are not driving to seconds behind a still standing concrete wall. The car in front of you has more or less the same breaking distance as you, so as long as you start breaking within those 2 seconds, you won't hit the car in front of you. The 2 seconds has nothing to do with kinetic energy formula, but with reaction time. That reaction time stays the same if you drive 10 kmph or 100 kmph Technically, if humans were robots with no reaction time, in a perfect world, cars could be driving bumper to bumper at 100 kmph, and if they all instantly brake at the same time, they would all stop perfectly fine. (mixed of significantly different mass to traction ratio like cars vs trucks should keep longer distance, and then E=½mv² is relevant.
The 2 second rule assumes the car in front of you isn't going to defy physics and come to an immediate stop. The 2 seconds is to account for reaction time to both determine the car in front is braking, apply the brakes, then realise how much the car in front is braking - then it assumes you'll both come to a stop at roughly the same rate. This is why trucks usually leave a bigger gap and why people who cut trucks off deserve their cars to be crushed into cubes with them still inside.
@ I learned three seconds distance. One for reaction time and two for stopping distance. And what you say about a concrete wall may not be so true. What often happens is that a car suddenly brakes hard for something. For every car behind it, they start braking later and later, untill they hit a massive lump of cars without even starting braking. Then we have very highly chances of fatalities in the cars in the middle of that lump of cars. And braking distance increases with the square of the speed increase. So when going faster, we should all increase the time distance to the cars in front of us. This is the reason higher speed gives or should give lower road capasity.
Bicycles, ebikes, electric cargo bicycles, robo taxis and escooters are great options for last mile, short distance travel. Reduced transportation costs and fossil fuels free transportation. Cities need to do more to encourage people to ride bicycles by providing SAFE, PROTECTED BIKE LANES and trails. Every adult and child should own a bicycle and ride it regularly. Bicycles are healthy exercise and fossil fuels free transportation. Electric bicycles are bringing many older adults back to cycling. Ride to work, ride to school, ride for health or ride for fun. Children should be able to ride a bicycle to school without having to dodge cars and trucks. Separated and protected bike lanes are required. It will also make the roads safer for automobile drivers. Transportation planners and elected officials need to encourage people to walk, bike and take public transportation. Healthy exercise and fossil fuels free transportation. In the future cities will be redesigned for people not cars. Crazy big parking lots will be transformed with solar canopies generating free energy from the sun.
Don't forget though that taxis (robo or human driven) travel a lot with zero passengers on board. Private cars for sure have a lot of downsides, but at least they usually have at least one person on board who actually have a reason to travel where the car travel. Sure, it happens that people give friends and family a ride, and then drive back home or whatnot, and the drive back home (or driving to a friend or family member to pick them up) is driving with zero "passengers" on board, but the percentage of driving distance of that must be way lower than taxis. TBH since there are hard regulations on taxameters on taxis, I think it would be reasonable to have a way higher road tax for taxis driving without passengers. This would create incentive for taxi companies to come up with IT systems that offer reduced prices for traveling along a specific route that a taxi anyways have to drive to pick up someone who called for a taxi, or for that sake have reduced prices for trips originating nearby where a taxi anyways is about to let a passenger off. I know that this might sound complicated, but it's a solvable problem well within the capabilities of IT today, and the one thing we know for sure is that if capitalism is presented with incentives to create a solution that increases profit, it will happen.
i already understood this concept but frankly the way you explained it here made it more confusing. You should talk more clearly about stop and go vs continuous flow at a higher level (a graphic would help). I was having trouble following the central message you were trying to push in part because it didn’t feel like you established your “thesis” well at the beginning of the video
Great video that gives useful tools to urbanists and safety advocates. Unfortunately in the US the problem is political. Ignorance itself is political, theres a reason we all grow up assuming gridlocked roads should just be expanded, while no one ever corrects us. Facts just do not matter to the voting public and politicians who rely on our ignorance to support their schemes.
Shouldn't the distance between cars (in seconds) be increased for higher speeds? The kinetic energy of the car and thus the breaking distance increase as a square function of speed. Yet this model uses a linear relationship between speed and distance between cars.
sure, but most traffic models assume just a 2 second spacing. The highway capacity manual uses the 1800 veh/hr based on the point particle assumption. Just to give you an idea of how unscientific the whole thing is! But, in reality all of these maximums are theoretical because were just never going to get close to these with imperfect traffic conditions. So trying to calculate everything perfectly is nice but not very helpful in the long run.
Hour is not an SI unit. only s for seconds is. People use it even in science because it's convenient and common. But technically if you want a bigger unit for time you'd have to use decaseconds, hectoseconds or kiloseconds.
Probably trying to minimize the political baggage that goes with being an urbanist, and just see people, cars, and bikes, rather than politics. Car centric city proponents are also urbanists, just not by the other side's definition.
_"Even if you get lucky and skip a red, the subsequent traffic lights will stop you getting too far ahead"_ Mathematically this isn't true. If you save 1 sec, and the traffic lights are modelled as random, then you have a 1/(cycle time) chance of saving (cycle time) secs, and on average you save 1 sec. This is the anecdotal wisdom you spent half the video railing against - 95% of the time you end up together at the next light, so it feels like you always do. In longer experiments you don't see big gains because people can't predict traffic well enough to get in the faster moving lanes etc and save that time; and there isn't that much time to save, maybe 5-10% which is less than 5 minutes per hour. It's also not a _helpful_ place to look for gains because aggressive drivers are less predictable, slowing everyone else down and decreasing safety. But there's no reason to be unscientific about it
Of course any lane is 1 car in 3 sec regardless of speed. But all this bs with bikes and trams turn it to 1 car in 30 sec. And of corse no sense in all these formulas. Seconds are always secomds, the safe distance measured in them, not length. At least while we have meatbags driving, not robots with shiny metal, ummm, heads. My new van can upkeep smaller distance with radar cruise, but it is not very safe drive.
I recently read "Order Without Design" by Alain Bertaud. It was a very dense but thought provoking book, which has a section on "mobility." He looks at it from the perspective of access, i.e. how many jobs can a person access in an hour from where they live (regardless of mode). Looking at it this way, speed does increase mobility as you would have access to more places within a certain timeframe (he uses an hour) when you are able to travel at a higher speed. A congested roadway might be able to move a similar amount of cars regardless of speed, but it lowers mobility in that a person has to spend more time traveling.
@KeesBoons it mainly looks at how many places you can access within a given time frame, so it doesn't really look at speed per se, just how long it takes to get from point a to point b, so I guess yes that would be average speed
Converse take: By making it easier to go farther, businesses will consolidate in more remote locations since their customer/employee-shed is larger. It's why America is the land of big box stores rather than small shops like other places. I've actually seen this happen in real life. In a river town south of me, they only had one grocery store on one side of the river, which drove a lot of traffic across the town's one bridge. So, naturally, they widened the bridge. A couple years later, another grocery story was looking to move into town on the other side of the river. But when they realized how easy it was to drive to the original grocery store from that other side thanks to the widened bridge, they felt like the competition wouldn't be worth it. In other words, if the town didn't widen the bridge (at great expense to the taxpayer), the problem would have solved itself! Transportation is a fine thing, but it shouldn't necessarily be an end to itself, especially in terms of economic impacts. It's a market distorter, first and foremost, and that's not always a good thing. It's great if it connects things that are far apart and can't reasonably be moved closer together (natural resources, adjacent communities, etc.), but if you're just doing it to generate more business, you're just spreading your economy thin more than anything.
@@Descriptor413 @Descriptor413 I would argue that the situation you describe is more a result of poor land use regulations that require low density single family development. You can still have density and great mobility (if you have good transit etc)
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
Recently had the experience of an impatient driver running a red light behind me, then pushing me and angrily waving at me in the rear mirror to speed up. When their was a two lane part he rushed past me. But the next few kms were trafficlight heavy area's all two lane, but no matter what he did, he never got much more than a few 100 meters in front of me. His angry-stressed- and frankly very dangerous driving got him to his destination 5 seconds earlier on a 15 minute trip than me, just patiently flowing with traffic.
I tend to believe, these people are in a rush to the end of their lives, but sadly also that of others.
I finally found an urban planning/transportation youtube channel that doesn't just make 50 videos on "car bad" with points that everyone else has covered already, and instead provides actual new content
Damn, never heard of CityNerd? You’re missing out. That said, I agree with the sentiment, the analysis is nice.
@@Co1010z I'll give them a go, looks like they're also covering new topics
I coast to a stop and gently accelerate. My fuel economy is great but all the suburban motorists hate me. Which is okay because I hate them even more.
Coast to a stop is great for fuel economy (on non-electric/hybrid cars), but accelerating slowly to save fuel was mostly a thing on old carburetor engine cars (I.E. approx 40+ year old cars) as they weren't as good at having the optimal fuel-air mixture, especially during acceleration.
(Technically a "gasoline engine" (really "Otto engine") is the most effictive at the point where you reach max power at a given RPM. I.E. pedal almost to the floor at the highest possible gear. There are a lot of caveats though, like for example cam/valve timing and whatnot, and modern (as in the last 20 years or so) cars have variable valve timing which complicates things).
Drivers ed in for example Sweden teach to accelerate swiftly and when accelerating fast enough skip gears. (Drivers ed is almost always done for manual transmissions). The reason is that this is actually more efficient.
@@Thesecret101-te1lm There's a guy from the UK who tested this thoroughly. Accelerating gently increases fuel economy as well.
@@ddrhazy Maybe it differs for different engines/vehicles?
@@Thesecret101-te1lm Doubtful. My own fuel economy shows as much when I accelerate gently in my 2019 Nissan Sentra. If I gun the engine to get it to the speed limit, the fuel economy is less than 7 mpg. If I barely touch the accelerator pedal, I can get it to 20 mpg. I don't do it on busy roads.
@@ddrhazy i think the idea is u are in the less efficient acceleration portion. U spend slightly more time at consistent really efficient speed. Idk tho would need testing
What is more, higher speed on muliti-lane stroads causes more traffic lights to be installed and average speed drops further
It is not high speeds that leads to signals. It is the increase in access points and traffic generators that require changes in assignment of right of way.
@ I agree that number of crossings with streets is main factor, what I meant permission for higher speed limits causes even more hardships for drivers to turn into such stroad, so usually, the most primitive solution to this problem is implemented- traffic lights. The real deal is a proper division of traffic into roads and streets like in the Netherlands
@@paweuutrzrzrz2699 Speed only matters when the road is not at full volume. If the road is at full volume, then it doesn't matter how fast the traffic is going. Perpendicular drivers can't cross or enter. Controlled junctions are added when roads are at full enough volume that this state occurs enough to be disruptive.
@traffic.engineer
That's why high-speed roads don't belong in urban areas. They should go around cities, not through.
@@traffic.engineer It's both... if you made a formula, both in combination would be variables leading to a higher number in traffic lights.
@9:54 did that bus driver just cast a spell to make the light turn green?
Nah, the Netherlands is just really well designed
@@Descriptor413 Designed so well that bus drivers can snap and change lights?
(I'm sure its just transit signal priority, but I thought it was funny how he snapped like that)
I do it all the time. It works! Sometimes 🤣
It is sensor based, but sometimes even high priority has to slow down for a second.
I play this game in the late hours on my bicycle. Pure fun, only one light forces me to a full stop every time.
Think I am going to write a big complaint to the municipality...
@@Sullyville It may seem like magic, but it's actually due to the efficient traffic management system. Especially at night, when you approach an empty intersection, the traffic light turns green just before you arrive. That's why I love driving in the Netherlands.
You should repeat the Douglas boulevard scenario but the driver incrementally decreases their max speed for each trial. Make a plot of average speed vs max speed to visualize the non-linearity.
you will get very few converts here in the US. A lifetime of being told that we are special and individualistic has taught most people that while driving they are an island in competition with everyone else on the road who is just in their way and that the goal is to always get in front of as many drivers as you can no matter where you are. Oh, at it has told us that it is cool to drive super loud cars very fast around other peoples neighborhoods in the middle of the night. Go USA #1!
10:12 Douglas Boulevard needs additional signs saying “You Are Averaging ONLY 30 mph”.
Filming your daschcam footage from inside of a bus?
You are an urbanist, my friend.
(Just discovered there is no bus emoji. Work of the "car conspiracy?")
🚌🚎
These are busses no?
And trams?
Driving aggressively >might< get you to your destination 'sooner', but the amount of energy expanded is exponentially higher and the recuperation time afterwards will be a net loss relative to any travel time gain.
I wonder if there's any scientific studies into this phenomenon.
In the Netherlands because the vast majority of traffic lights are sensor based, aggressive driving in some places can net you a time benefit. Also, because you may be able to squeeze yourself into an earlier traffic light cycle. But this varies a lot depending on the location, traffic volume, and configuration of the lights and such. It's also just plain wasteful.
Hi Celis C, what are trying to do is pure science!, all your need is careful critical oversight of the information you use for your calculations and sensible reliable observations, do your best to exclude subjective assumptions and then allow your brain to think to all through, at some point it will offer the outline of an explanation that correlates with your observations.
the next part is to formulate what you come up with into a useable hypothesis which you can then test, the easier it is to test and thus refute the better it is!. All you require for total refutation is just one bit of empirical evidence that confounds the hypothesis which you then abandon and wait for a new one, each time you go through this process you learn another thing that is not true, a properly proven fact, this way you increase your total body of knowledge.
In this particular context we can start with a number of scientific principles which we accept as established, these include the given assumptions that the greater the speed of the traffic the more vehicles pass any given point at any given time the greater the total traffic flow, one reason for this is that while the lenght of each vehicle does not vary with speed the distance between them does, in fact with any given number of vehicles of any specific length there is a minimum threshold below which there is no space between them at all at everything stops, it then takes a finite amount of time for them all to start moving again further reduce the flow rate.
From all this it follows that fewer shorter vehicles all travelling at a constant speed with the same minimum space between them would be optimal, that however is the 'perfect' state scenario which for very good reason can never happen because reality includes variation and diversity, these factors are much more difficult to enumerate but that is not needed!, allm tht is needed is effective traffic control that reads the flow rate and as it drops reduce the vehiclers allowed on that road, when the flow rate rises again near to the proximate optimal threshold more vehicles can be allowed to join.
From that in situations where the backlog at the access ramps become too much other measures must be applied, there is an obvious range of options all the way from reducing the size of vehicles to adding more lanes and building new roads or as a last resort providing adequate public transport using its own part of the road network so that travellers sitting waiting in a car for a space on the road will see bus after bus not full of passengers passing them and they can make their own choices.
The manner in which each of us choose to drive has little or no material effect on the whole traffic pattern, it might be 'true' that if all drivers applied exactly the same style we could get more traffic on the same roads but they don't and they won't all do the same as each other. Regardless of political ideology we should be just rational and practical.
Cheers, Richard.
@@wewillrockyou1986 I don't think he just means fuel energy. Aggressive driving makes you angry and frustrated, which costs so much more mental and emotional energy for only a minute gain on a 30 minute trip.
I always laugh at cars on the high way, push me to the side, speeding up only to be stuck behind the next car they have to push again. In the end they exit the high way only a minute before me, but are a thousand times more frustrated....
Ive often wondered about this, figuring that increased speed must improve capacity, but get balanced out by greater following distance. It was really nice to see you sit down and go through the numbers. Subscribed!
When you say "following distance" most US drivers scratch their heads and say "what is that?".
→ 3:38 Please use a better multiplication sign - at least one which is centerer. A centered dot (·) works, or even a centered diagonal cross (×). But this six-pointed raised asterisk (maybe a font variant of *?) is definitively not a multiplication signs (at least use the centered one (∗), if you must). - 5:27 Somehow you here managed to arrange the asterisks with the center line here?
→ Another part to consider is whether the 2 seconds of following distance is actually safe enough with higher speeds. I think you'll actually need more distance to be able to safely stop in case of an accident in front of you.
2 seconds is the distance they teach you at drivers lessons here in the netherlands (where the youtuber is from)
Love you point about not being an "urbanist" and the service your channel provides.
It wasn't long after I discovered NJB that I thought, "ok, cars are bad, but I want to actually argue with engineers about why things need to change in the US." I wanted to know the actual math.
Thanks for providing this side of the narrative. I think you're one of the few RUclipsrs doing it.
Putting engineers in charge of decisions that are political decisions not engineering decisions is part of America's problem you shouldn't have to argue with an engineer about this the engineers should be told what to build and their job is to figure out how.
@@supermanifolds You can't order someone to beat physics. So no, engineers need to have a say in things. And by the way...how do we determine what our orders to engineers look like?
Mind you, it is not a theoretical question. In Canada, we see exactly that kind of thing being played out right now. A politician, probably with reasonable backing by his voters, orders bike lanes to be removed.
@@supermanifolds Whereas I think these decisions should be made by engineers, not politicians. Maybe politicians can set general goals, but as they usually do not understand how these things work, they should be as far from the actual decisions as possible.
NJB does not say "cars are bad". The point he makes is that car centric infrastructure development is bad.
Recommending the book "killed by a traffic engineer" by Wes Marshal
In the UK, the Highway Code requires driver to drive within their stopping distance which is a quadratic relationship to speed due to Kinetic Energy being proportional to the square of velocity. In you model you used a linear relationship. If you had used the quadratic relationship you would got the answer that slower speeds always increase capacity. You can see that in action in reverse: when traffic increases speed naturally decreases (congestion) to accommodate the need to increase traffic capacity.
A moving car does not suddenly stop from one moment to another. It is bound by inertia and will slowly come to a stop in a reasonably similar way to the following car. Your distance only needs to account for your own reaction time, so 2s is reasonable. And at least here in Germany it is explicitly coded into law. Probably in the Netherlands as well.
Looking at existing traffic out in the world, 2s seems like a gross overestimation. At highway speeds this should turn out to around 60m, but I often find traffic on the left lane too bunched up to even attempt fitting a 5m long car into the gaps ;)
Except in motorway conditions this is tricky. The 2 seconds rule is to account for delays due to reaction speed, but also taking into account that the car in front is not stationary and has its own stopping distance. In reality it would already be great if people kept the 2 second distance on the motorway. For urban traffic the stopping distance is more important, but when adding reaction speed 2 seconds is a good rule of thumb for normal conditions.
Kinetic energy going up by the square of speed is not the reason why stopping distance goes up by the square of your starting speed. That correlation is a myth!
Stopping distance can be calculated by multiplying the time it takes to stop, by the average speed. And increasing the starting speed increases both the time _and_ average speed.
For example, lets assume we have a car that can brake at a constant rate of 5 m/s/s.
If we start at 10 m/s, then it would take 2 seconds to come to a stop, and our average speed would be 5 m/s. So our stopping distance would be 2s * 5m/s = 10 m.
If we start at twice that, 20 m/s, then it would take twice the time (4 seconds) and our average speed would also be doubled (10 m/s). So we get 4s * 10m/s = 40 m.
If you want a visual, then we can plot this on a graph with speed on the vertical axis, and time on the horizontal. With a constant rate of deceleration like in the examples I gave, then we'd get a straight line with a downwards slope. And the area would be triangle shaped, hence why the average speed is just half the starting speed. (And I'm ignoring drag and the slight lift most cars get from being airfoil shaped. As they roughly cancel out.)
And _most_ land vehicles generally have close to constant deceleration when braking. As the resistance from friction (both in the brakes and tires traction) goes up with speed at the same rate as kenetic energy does. And perfectly cancels it out, making the exponential nature of kenetic energy a non-factor in stopping distance.
@@PauldeVrieze The car in front might not instantly stop but another car might pull into your lane or a pedestrian might step out.
Either way Rule 126 says "You should leave enough space between you and the vehicle in front so that you can pull up safely if it suddenly slows down or stops. The safe rule is never to get closer than the overall stopping distance (see Typical Stopping Distances diagram)".
The stopping distances in the diagram show reaction distances increase linearly with speed but the braking distances increase by the square of speed.
@@vulduv The official braking distances in the UK go up according to a square law and it is those distances together with a linear thinking distance that UK drivers are required to leave between them and the car in front.
At 32 km/h the thinking distance is 6m and the braking distance is 6m giving an overall stopping distance of 12m.
At 64 km/h the thinking distance is 12m and the braking distance is 24m giving an overall stopping distance of 36m.
Whatever you might think, these are the gaps that UK drivers are required to leave.
It’s great to explain these mobility concepts. Would be good to also explain how travel time is only marginally reduced as speed increases (between fixed points). And energy increases exponentially…
Suggestion for future topic:
What are the actual effects of "green wave" traffic lights? I.E. ensuring that a bunch of traffic lights along a major roads are green at each junction for traffic that isn't turning?
Also re 1+1 roads (without overtaking abilities) v.s. 2+2 roads:
I would say that it's not just about aggressive driving and whatnot. It's also about calm driving. It at least feels way less aggressive to set the cruise control to the legal speed limit (where that is actually reasonable) and overtake everyone who thinks their speedometer is showing actual speed, and thus drives 26km/h on a 30km/h road.
Modern cars have automatic distance adaption for their cruise controls, but older cars don't, while at the same time even older cars tend to otherwise have excellent cruise control (kind of thanks to drive-by-wire being the norm for the last 25 years or so). Driving without cruise control also takes away attention from traffic as you every now and then need to check your speedometer.
Also re 1+1 vs 2+2 roads: At least in Europe it's fully legal (and I think this is great) for vehicles to be "underpowered", as in a car with say 100-120hp are allowed to haul a total of 3.5t (car + trailer), and those will obviously accelerate slowly, and in that situation 2+2 is great. Sure, a rare case, but not unheard of.
That's one reason junctions have more lanes that merge back into one
You are assuming people won't just fill both lanes and travel at the same speed. It happens here all the time. I've been on a 3 lane road trapped behind 3 cars all doing about 15 under the limit, all in their own lane.
SOme 30 years ago such a system was installed on a road in Southampton. Whilst on a course in the centre of town I car shared with someone who knew all the short cuts around the traffic queues. We shot right at junctions , sswung left at others, raced down side streets , stopped at traffic lights and got to the destination. I was timeng the drive unknown to the driver.
The next day it was my turn, I followed the green wave on the main road, at the moderate speed allowed, with few gear changes needed and little braking. We arrived 5 minutes quicker than the day before.
Nice opening, the first 12 seconds of the video is Delfgauw, next to my hometown of Delft
Great video !
Max Traffic Flow: *Is 1800 cars/hr*
Tailgaters in giant pickups: "That won't stop me. I didn't read the driver's manual."
Jokes aside, how do traffic engineers compensate for areas where the majority of drivers are aggressive drivers that won't hesitate to break the law? Where I live 5-20 mph over the speed limit is normal (it actually becomes dangerous at times to try to do the speed limit), weaving between lanes is increasingly common, hogging intersections is common, and the general attitude is "the police can't stop us all".
Simple, make the roads more hostile to driving (and reduce hostility in areas where people drive nicely)
Just like how you train a dog (cuz that's how these people behave.
You drive fast: you loose a bumper
You drive slow: one less speedbump for you.
(there are lot more things you can do that speed bumps of course, like narrower roads, less smooth paving, more turns, on road obstacles, traffic lights, speed cameras, roundabouts etc.)
Road width is the most common thing designed wrong in areas where speeding is too high. The narrower the road the faster you feel you're driving. So if the road feels like a 60mph road but the sign says 40mph, people are going to drive 60 even though those that don't necessarily want to break the law on purpose.
@@DrTheRich Speed bumps don't really encourage slow driving away from the speed bump though. They barely encourage slow driving on the speed bump these days. They kinda worked back when most people drove cars with very little power, but nowdays most cars can do 0-100 kmh in under 8 seconds, and any speed bump that'll break the spine of anyone in a hatchback doing 30 will barely be noticed by someone in an over-sized SUV doing 40. They incentivise buying more dangerous vehicles. Now lane narrowing, chicanes, roadside clutter (tall roadside clutter so SUVs will notice it) are probably better tools.
Speaking of SUVs really make everything around you seem further away. I find it much harder to judge my speed in them - though I haven't driven that many. Maybe we should just ban them all together and fix that problem.
Very interesting video! One factor beyond traffic flow to keep in mind though is the time saved by individual road users when they get to go faster. Time-efficient travel drives economic growth, which is why humans have always strived to find faster ways to travel: railroads, highways, freeways, airplanes, bullet trains, ...
Of course, there is a balance to be found where accidents on ill-adapted infrastructure will also negate these economic gains after a certain point. Furthermore this applies more to long distance travel rather than core-urban travel, but it still matters
The engineers know that theoretically, speed for freeways has no impact on maximum capacity. However, at higher speeds, this reduces the average amount of time one vehicle spends IN the system, meaning that the system will clear up sooner for OTHER drivers to use it. For example, if the free flow speed on a freeway was 20mph instead of 80mph, that means on average, each vehicle is spending 4 times longer in the system, meaning any additional vehicles that want to enter the system have to wait 4 times as long to get a "spot". While not affecting freeway capacity in the literal sense, it is easy to see how increasing the average speed on the system improves things. It's all about clearing the system as soon as possible for other vehicles to go and use that capacity, which is something transportation engineers must also take into account. The lack of effect on freeway capacity is a result of how capacity is defined, not evidence that increasing speed is useless and counterintuitive. There are real benefits, even though there is also a real cost (increased fatality rates).
The same can be made for the argument against adding lanes to freeways or roads. Engineers also understand that adding more lanes will not usually lead to any long term benefits in travel time, but it does (up to a point) improve highway capacity, meaning that even though it will still take you 20 minutes to go from point A to point B, regardless of whether the road has 3 or 4 lanes, the road with 4 lanes will be able to carry more vehicles per hour at that speed, whereas before, with only 3 lanes, it was unable to carry that capacity which led to a reduction in highway level of service. And obviously, if you've ever driven on a road that has more than about 4 lanes in one direction, you realize experientially the inefficiencies that arise that result in diminishing returns from adding additional lanes, especially in a high ramp density segment of the freeway. It turns into chaos, and is more dangerous, and at some point, the massive costs outweigh the additional capacity of another lane. Because of all of these things, adding a 16th lane is a lot less useful and more expensive in the long run than adding a 3rd lane.
As for your stop and go traffic analysis, I have nothing to say because I think you explained it better than I could. And I also don't like our reliance on motor vehicles, and I think major metropolitan cities like Atlanta and Houston are enough evidence that designing primarily for cars is a bad idea. However, it IS more complicated than that, and youtubers like "Not Just Bikes" don't seem to understand this. Many cities now are simply too low density to use anything but cars or rapid transit, but public transportation is awful here in America. In my opinion, the way to go forward for American cities is to start making downtowns inaccessible to cars, and cordon off downtowns into pedestrian and emergency / commercial vehicles only. Reduce the size of these vehicles to their european counterparts that still function well enough, and then you can start narrowing roads and getting rid of all of that asphalt. You can add some green space and even have some street markets in the middles of these roads, and building pedestrian friendly spaces. You can have multi-story parking garages on the outside of this area and make use of the 3rd dimension instead of these horribly large and inefficient parking lots. Eventually, as funds allow, these buildings can be expanded into the street, or courtyards can be added. You can have public transit going to downtown, and creating more of these car-inaccessible spaces and treating cars more as transportation between two areas instead of as a mobile base will be helpful. Not everywhere in a city needs to be accessible for cars.
In the meantime the suburbs could also be made more liveable by allowing local shops and restaurants to operate there. More people will use sidewalks if there are destinations where people actually want to walk to. And if more people walk, more people will ask for additional sidewalks (and bicycle paths).
I live in a quarter of a (Dutch) city that was built in the 60s. When this country was still firmly on a car-dependent path. They built high rise apartment buildings, family homes and schools and planted some trees, but hardly any shops. These were retrofitted much later. Nowadays everyone in this quarter lives within walking distance of a cluster of 3-4 shops (bakery, vegetables, butcher, convenience shop, café/restaurant, drycleaner and/or a small supermarket). And there is a larger shopping mall with larger supermarkets, clothing shops, book store, drugstore etc. in the middle of the city quarter. From my home it's a 2 minute walk to the closest supermarket and butcher, 4 minutes to a bakery and snackbar and a 5 minute bicycle ride to the shopping mall.
Because the shops are so close by, people can stay in their homes longer. My neighbour is 86 and can't drive a car anymore, but she can still do her shopping with her walker. Of course we help her when she needs something from the large mall or when the streets are icy (and too slippery for her), but I think it's nice that she can stay in the house she's lived in since in for the past 60 years, without losing her independence.
Your math makes zero sense. "the average amount of time one vehicle spends IN the system" means literally the same as "cars per minute" aka the same formula applies as in the video.
you just describe it it a more convoluted and wordy way to be able to arrive at an incorrect conclusion
Great content! Love the explanation of the math behind this stuff. Subscribed!
I was surprised this morning to learn that my RUclips algorithm had not brought me to Not Just Bikes
I have often checked the average speed record for my car. Over nearly 1000 miles I seem to average 36mph, in spite of most of my journies being at motorway speeds.
I once left the Warwick services on the M40 to travel to Portsmouth. My employer left at the same time. He always drive at an indicated 80 mph, I never drove more than indicated 70, on motorways and dual carriageways. When we reached the destination , about 140 miles, my employer was just getting out of his car as I pulled up behind him. He had needed to wait at one set of traffic lights whilst I had not.
The use of * instead of either · or × is kinda driving me nuts. * is the symbol for the convolution, after all.
Is the assumption of constant following time with speed empirically derived?
Assuming a linear increase of following distance with speed is wrong if you assume everyone drives safely. In Germany we learn to keep a distance that is greater than reaction distance plus breaking distance. Reaction distance increases linear with speed, breaking distance quadraticly. We learn the following approximation for the distance you should keep: (speed / 10 km/h)^2 meters
If you use this approximation, there must be an optimal speed where the capacity is at a maximum before the quadratic exceeds the benefit due to vehicle length and additional speed reduces the capacity again.
Edit: According to my calculations, the optimal speed is about 22.36 km/h with a road capacity of about 2236 per h.
(The exact optimal speed is (square root of 500) km/h. The 500 comes from the 5m vehicle length and the square of the 10 from the approximation for breaking distance.)
You can do the calculation without having to need the approximation. You do need to chose a braking decelaration though.
Assuming 5m/s² (and car length 5m), the ideal speed becomes 7m/s (= 25,2 km/h) with a max theoretical throughput of 2230 cars/hour
30km/h => 2204/hour
50km/h => 1847/hour
70km/h => 1499/hour
Very similar results.
Also interesting: if self driving cars don't need reaction time (because they communicate in advance).
The capacity for a 50km/h speed would increase to 2058 cars/hour (increase of around 11%)
The formula F = s*d*t is misleading. The units don't match up (s is in distance/time, d is distance, t is time/time (seconds per hour)) which multiplies to distance^2/time, where you actually want 1/time (rate of cars per unit time). But when you do the formula example, you express following distance as "1 car per 27.8m", which is actually _dividing_ by following distance, not multiplying. So it should be s*t/d. If this is some traffic engineering formula, then maybe this discipline should get better with tracking units. Because it seems like you're treating the quantity "following distance" as an _inverse distance_ (units 1/m) rather than a distance, which is just confusing.
Also, having "t" as a unitless quantity (time / time) is also deceptive. Why not just say that the car capacity rate is F = s / d, which gives you units of (time)^-1, and then just adjust the units accordingly. So if you have s in m/s, and d in m, then you get cars/second, and then just multiply by 3600 to get cars/hour.
So how do you fix these terrible intersections? It's brutal sitting at a red light when no one is coming the other way.
Install roundabouts. No stop required, just yield.
Use smart traffic lights that have sensors to detect traffic and react accordingly, or install roundabouts if feasible.
(smart) roundabouts, over/under passes, merging lanes, rerouting traffic in smarter ways, reducing need for cars, lower speeds. If you play any city planner game, you'd realize that hard time-regulated traffic lights are amongst the worst naive solutions to solve a car crossing.
Nice video. You said that the Dutch have two different manuals; one for urban, and one for rural. What are the names of the manuals, if you don't mind?
The CROW manuals. There is a whole bunch of them, so have a look on their website(s), which are available in english.
Good video. Mythbusters did an episode comparing agressive lane switching to flowing with traffic on a highway if you are looking for more visual examples.
Idea for a next video: ideal distance between bus stops on a straight line for 30, 50 and 70km/h compared to population density. (you may assume an infinite amount of buses and passengers and their destinations are distributed evenly)
Walking speed = 1m/s
deceleration and acceleration = 3m/s² (or if you can find a more accurate number you can use that)
Regarding the following distance/time given at 3:56, how would self driving cars affect the variable? How much could self driving cars feasibly reduce the distance under 2 seconds?
2 seconds is the best case scenario WITH self driving cars. Self driving cars can reduce things like distracted driving when a car waits a second or 2 longer than it should to drive out of a cue. Or to get a bit closer. But theres still a minimum following distance so a car has time to stop if the car in front of it gets a crash and comes to a full stop.
If you want to be more efficient, you might as well get out of the car and onto a bus since thats the only way you can start fitting more people in per square meter/foot.
@ Thanks for the response!
So I presume that 2 seconds is what you get if you assume instantaneous reaction when the car in front stops?
pretty much
@@buildthelanes Re having margins to stop if the car in front ends up in a crash - this might be the spiciest take ever, but given that cars have a theoretical capacity of about 4-6 people, while a bus can have 10x as many passengers, and thus it's reasonable for approximately 10 cars to crash into each other if a crash would happen, as it affects about as many people. In practice things like outcome of accidents and whatnot has to be considered. But the thought provocation is that it's more disruptive if a single bus ends up in a crash than if 5 cars crashes. In particular at low enough speeds, i.e. at 30km/h, it might be reasonable to actually have drivers drive close enough that pile-up crashes are unavoidable.
(At low enough speeds there aren't even any noticeable damages if cars crash into each other. Can't remember the details but IIRC US regulations require this for 5mph, and it seems like this has been adopted world wide. In other words, at 5mph it would actually be reasonable to require drivers to drive onto the bumper of the car in front, to maximize capacity).
Also re self driving cars:
A major missing part about self driving is "hive mind". If there were provisions specific for self driving cars in the telecom mobile phone systems, to let them have a "hive mind", it would be super easy to have long stretches of cars slow down if an accident/incident happens. The self driving cars could also have a display turning on stating "slow - accident ahead" warning drivers of non-self driving cars.
Another "hive mind" feature would be parking. If every car on a street in a city is self driving with a "hive mind", they could park in each other and just stop in the middle of the street, until a car needs to move, and then those who are in the way would just drive around the block like lemmings. Given that electric cars use very little energy when driving really slow this actually seems like a good way to increase parking space efficiency in cities.
This is a great question, I wasn't thinking it myself but I wish I had been. Thanks for answering, Stephan! Greetings from a fellow Dutch American Stephen.
More speed means less time for people to merge on a road , right? So the higher speed traffic goes the less merging, do less capacity
I do wish the "distance" was presented as an inverse of distance in the a a beginning. I had to go back to figure out what you were talking about. It's strange that you call the amount of cars per unit distance "distance". Thanks for the otherwise clear and concise video.
Retail bicycle outlets need to do more to encourage young people and older adults to ride bicycles.
Sponsoring bike trains to escort children on their rides to school would be a great start. Organizing volunteers, teachers and other to ride along would be a great start. Getting children out of minivans and onto bicycles would be healthy exercise, build independence and make society healthier.
Fun ride should also be organized. Getting a local bike club or school to sponsor an annual event to a local park or trail would encourage both adults and children to ride bicycles. Getting local elected officials to help with sponsored activities would help to educate them about the need for safe, protected bike lanes and trails in their community. Offering space and coffee for local riders to meet up would also improve store traffic.
I would not let my kid ride a bike in the city, or most american towns. Its simply too dangerous. Pedestrians and Bicycles are among the fast growing fatality rates in the entire transportation system. Rides are great, but the city has to make actual efforts to develop cyclist protection before people would feel safe doing so.
@@cadenorris4009 That is why safe, separated bike lanes and trails are needed. It is so older adults and children can ride bicycles safely separated from cars.
I worked for a construction company in The Netherlands and they bought a plot of land in France to build a holiday bungalow park, outside town. The entrance of the park is at a departmental road where you can drive about 90km an hour, not an ideal road for cycling. And certainly not one I wanna risk my life cycling on. In order to sell the bungalows to Dutch people they asked the municipality to provide a separate cycle path from the park to town. It took almost 2 years to get the cycle path, because it isn’t (or wasn’t) common practice to provide separate roads for cyclists in France. But they wanted to accommodate the bungalow owners because they could revive a dismal local economy. It is great to be able to cycle 20min to the local bakery to get fresh bread every morning instead of getting it by car. A great daily exercise. It’s sad that there no other cycling paths in the area. It would be great to cycle around the area instead of sightseeing by car.
It has little to do with people not wanting to cycle. It has everything to do with road design.
It is an inverse relationship. More density decreases speeds, less density increases speeds. Optimal capacity is a calculated balance between volume and speed.
Nice food for thought
Well done! Thanks!
Hope you get a lot of, same level, engineers to get useful discussions going!
Best wishes for 2025!
Capacity constraints not typically faced by bicyclists.
Here’s a consideration. Optimal conditions for maximum throughput. I’m talking professionals racing on a closed course. A 33-car Indycar pack at The Brickyard can probably fly by, all bunched together on the opening lap in… I dunno, 10 seconds? Meanwhile, the 176 members of a Tour de France day 1 peloton during the leadup to a sprint finish can go by in a similar amount of time. That’s more than 5x the amount of cyclists, and at the Tour, this is usually on public roads maybe half the width of the Indianapolis Motor Speedway.
Obviously real world conditions do not reflect race conditions. Nevertheless, the difference is striking.
@Build the Lanes, best video yet. Can you do the same for an intersection capacity/hr in relation to lanes, through and turn?
Thank you!
Wait.
For the freeflow thing, the time between cars (even if we asume them to be dots) its not the same for every speed. Higher speeds typically mean less time between cars (it doesnt increase lineraly with speed)
A question related to the video (and not to the point you’re making): Why were you driving a bus on the 455 (and 32(?)) bus lines? Did Haarlem not trust you to drive a bus closer to home/work/in own province 😋?
I would expect higher speeds reduce capacity at some point because psychologically people would end up keeping longer distances to the preceding vehicle at higher speeds. My basis for this is observing driving on the autobahn, on average people seem to keep better to the 2 second rule at speeds of over 150 or so.
that's why he said 2 seconds and not 2 meters...
That way it includes the longer distance at higher speeds. And an average of 2 seconds foor 100+ speeds seem fair too, because too many people sadly (including me admittedly) drive closer than that even, especially at a busy time.
what about highways on which cars can actually overtake each other, and assuming everyone stays right except to pass
My burning curiosity is this: can "smart", "networked", or "AI" intersections improve throughput significantly? My second burning curiosity is do lane jumpers increase decrease or not affect traffic throughput. Thanks for your answer, kkbye.
*FEEDBACK*
Yes, the video does help. It's not an interest of mine, but it does help me a bit to become more knowledgeable. I don't think that it's too useful, though.
*TOPIC REQUEST*
I recall a guy sharing his discovery that slow driving in the right lane unplugs traffic jams much more quickly, as opposed to fast driving in either lane. It was so counter intuitive, but he somehow explained it.
If you know that this is true, then would you explain it, please? Perhaps it incentivizes fast people to stay on the left.
You should really look into manim for the math equations.
Holding 2 seconds distance while going 70 - 90 km/h is nuts. And when all cars in a long row hold 2 seconds distance, it is a catastrophy waiting to happen.
The formula for kinetic energy EK=0.5mvv is the key, here. Speed has the squared impact on it.
It's not nuts, is a common thought practice in driving schools across the world for highway driving.
The thing you are forgetting in your thinking here, is that you are not driving to seconds behind a still standing concrete wall. The car in front of you has more or less the same breaking distance as you, so as long as you start breaking within those 2 seconds, you won't hit the car in front of you.
The 2 seconds has nothing to do with kinetic energy formula, but with reaction time. That reaction time stays the same if you drive 10 kmph or 100 kmph
Technically, if humans were robots with no reaction time, in a perfect world, cars could be driving bumper to bumper at 100 kmph, and if they all instantly brake at the same time, they would all stop perfectly fine.
(mixed of significantly different mass to traction ratio like cars vs trucks should keep longer distance, and then E=½mv² is relevant.
The 2 second rule assumes the car in front of you isn't going to defy physics and come to an immediate stop. The 2 seconds is to account for reaction time to both determine the car in front is braking, apply the brakes, then realise how much the car in front is braking - then it assumes you'll both come to a stop at roughly the same rate. This is why trucks usually leave a bigger gap and why people who cut trucks off deserve their cars to be crushed into cubes with them still inside.
@ I learned three seconds distance. One for reaction time and two for stopping distance.
And what you say about a concrete wall may not be so true. What often happens is that a car suddenly brakes hard for something. For every car behind it, they start braking later and later, untill they hit a massive lump of cars without even starting braking. Then we have very highly chances of fatalities in the cars in the middle of that lump of cars.
And braking distance increases with the square of the speed increase. So when going faster, we should all increase the time distance to the cars in front of us.
This is the reason higher speed gives or should give lower road capasity.
Bicycles, ebikes, electric cargo bicycles, robo taxis and escooters are great options for last mile, short distance travel.
Reduced transportation costs and fossil fuels free transportation.
Cities need to do more to encourage people to ride bicycles by providing SAFE, PROTECTED BIKE LANES and trails. Every adult and child should own a bicycle and ride it regularly. Bicycles are healthy exercise and fossil fuels free transportation. Electric bicycles are bringing many older adults back to cycling. Ride to work, ride to school, ride for health or ride for fun. Children should be able to ride a bicycle to school without having to dodge cars and trucks. Separated and protected bike lanes are required. It will also make the roads safer for automobile drivers. Transportation planners and elected officials need to encourage people to walk, bike and take public transportation. Healthy exercise and fossil fuels free transportation. In the future cities will be redesigned for people not cars. Crazy big parking lots will be transformed with solar canopies generating free energy from the sun.
Don't forget though that taxis (robo or human driven) travel a lot with zero passengers on board.
Private cars for sure have a lot of downsides, but at least they usually have at least one person on board who actually have a reason to travel where the car travel. Sure, it happens that people give friends and family a ride, and then drive back home or whatnot, and the drive back home (or driving to a friend or family member to pick them up) is driving with zero "passengers" on board, but the percentage of driving distance of that must be way lower than taxis.
TBH since there are hard regulations on taxameters on taxis, I think it would be reasonable to have a way higher road tax for taxis driving without passengers. This would create incentive for taxi companies to come up with IT systems that offer reduced prices for traveling along a specific route that a taxi anyways have to drive to pick up someone who called for a taxi, or for that sake have reduced prices for trips originating nearby where a taxi anyways is about to let a passenger off. I know that this might sound complicated, but it's a solvable problem well within the capabilities of IT today, and the one thing we know for sure is that if capitalism is presented with incentives to create a solution that increases profit, it will happen.
_"Although the following distance changes according to the speed, the length of the car stays the same."_ Einstein:
Light speed traffic congestion....
Just another reason why cars approach a point mass as speed increases
i already understood this concept but frankly the way you explained it here made it more confusing. You should talk more clearly about stop and go vs continuous flow at a higher level (a graphic would help). I was having trouble following the central message you were trying to push in part because it didn’t feel like you established your “thesis” well at the beginning of the video
bump
Great video that gives useful tools to urbanists and safety advocates. Unfortunately in the US the problem is political. Ignorance itself is political, theres a reason we all grow up assuming gridlocked roads should just be expanded, while no one ever corrects us. Facts just do not matter to the voting public and politicians who rely on our ignorance to support their schemes.
Shouldn't the distance between cars (in seconds) be increased for higher speeds? The kinetic energy of the car and thus the breaking distance increase as a square function of speed. Yet this model uses a linear relationship between speed and distance between cars.
sure, but most traffic models assume just a 2 second spacing. The highway capacity manual uses the 1800 veh/hr based on the point particle assumption. Just to give you an idea of how unscientific the whole thing is!
But, in reality all of these maximums are theoretical because were just never going to get close to these with imperfect traffic conditions. So trying to calculate everything perfectly is nice but not very helpful in the long run.
27.8m/91ft is a lot
If you try to use SI, please use "h" for hour, not "hr" 😉
Hour is not an SI unit. only s for seconds is. People use it even in science because it's convenient and common. But technically if you want a bigger unit for time you'd have to use decaseconds, hectoseconds or kiloseconds.
Usa 30kph is parking lot speed
I don’t understand this need to specify that you’re not an urbanist? You do realize that urbanism is not just RUclips videos right?
Probably trying to minimize the political baggage that goes with being an urbanist, and just see people, cars, and bikes, rather than politics. Car centric city proponents are also urbanists, just not by the other side's definition.
_"Even if you get lucky and skip a red, the subsequent traffic lights will stop you getting too far ahead"_ Mathematically this isn't true. If you save 1 sec, and the traffic lights are modelled as random, then you have a 1/(cycle time) chance of saving (cycle time) secs, and on average you save 1 sec. This is the anecdotal wisdom you spent half the video railing against - 95% of the time you end up together at the next light, so it feels like you always do. In longer experiments you don't see big gains because people can't predict traffic well enough to get in the faster moving lanes etc and save that time; and there isn't that much time to save, maybe 5-10% which is less than 5 minutes per hour. It's also not a _helpful_ place to look for gains because aggressive drivers are less predictable, slowing everyone else down and decreasing safety. But there's no reason to be unscientific about it
Also.. ;)
We use bikes ( Notjustbikes )
xD
Of course any lane is 1 car in 3 sec regardless of speed. But all this bs with bikes and trams turn it to 1 car in 30 sec.
And of corse no sense in all these formulas. Seconds are always secomds, the safe distance measured in them, not length. At least while we have meatbags driving, not robots with shiny metal, ummm, heads. My new van can upkeep smaller distance with radar cruise, but it is not very safe drive.
I recently read "Order Without Design" by Alain Bertaud. It was a very dense but thought provoking book, which has a section on "mobility." He looks at it from the perspective of access, i.e. how many jobs can a person access in an hour from where they live (regardless of mode). Looking at it this way, speed does increase mobility as you would have access to more places within a certain timeframe (he uses an hour) when you are able to travel at a higher speed. A congested roadway might be able to move a similar amount of cars regardless of speed, but it lowers mobility in that a person has to spend more time traveling.
I hope Alain was bright enough to consider the difference between average and maximum speed.
yes higher speeds reduce travel time when they are not congested but they dont move more vehicles per hour
@KeesBoons it mainly looks at how many places you can access within a given time frame, so it doesn't really look at speed per se, just how long it takes to get from point a to point b, so I guess yes that would be average speed
Converse take: By making it easier to go farther, businesses will consolidate in more remote locations since their customer/employee-shed is larger. It's why America is the land of big box stores rather than small shops like other places.
I've actually seen this happen in real life. In a river town south of me, they only had one grocery store on one side of the river, which drove a lot of traffic across the town's one bridge. So, naturally, they widened the bridge.
A couple years later, another grocery story was looking to move into town on the other side of the river. But when they realized how easy it was to drive to the original grocery store from that other side thanks to the widened bridge, they felt like the competition wouldn't be worth it. In other words, if the town didn't widen the bridge (at great expense to the taxpayer), the problem would have solved itself!
Transportation is a fine thing, but it shouldn't necessarily be an end to itself, especially in terms of economic impacts. It's a market distorter, first and foremost, and that's not always a good thing. It's great if it connects things that are far apart and can't reasonably be moved closer together (natural resources, adjacent communities, etc.), but if you're just doing it to generate more business, you're just spreading your economy thin more than anything.
@@Descriptor413 @Descriptor413 I would argue that the situation you describe is more a result of poor land use regulations that require low density single family development. You can still have density and great mobility (if you have good transit etc)
just use a train duh