Great video, It's amazing (and somewhat scary) just how many drivers how no idea how to stop a modern car and have never actually tried to do so! If i may, i'd add three additional points: 1) LOOK WHERE YOU WANT TO GO!! Really, really, really important, and really, really, really hard to do in a true emergency, where naturally you'll look at the thing you are trying to miss! But, you need to look around it! Many people simply brake, fail to steer and pretty much drive into the object in their way, despite there often being an entirely clear carriageway giving an easy path around said obstruction. The only way to learn this is to practice it ime. 2) Much less important, but in a front wheel drive car, and especially if it's slippy under tyre, you will stop in a significantly shorter distance and with better steering control if you put the clutch in immediately you commence the emergency braking. It's not crucial, it's a more advanced technique, and often gets forgotten, but decoupling the engines inertia (referenced to the front wheels by the gear you are using) from the braking event will allow the ABS to operate faster and more efficiently. In the worst case, in snow or ice, the difference in stopping distance can be measured in 10's of meters! 3) Hopefully you'll never need this one, and if you do, most people won't have time or the ability to carry it out, but if you are in the middle of an real emergency braking event but realise you are NOT going to stop, and are going to hit a large solid object at speed, then it's better to get off the brake (And clutch) pedal at the last possible second to avoid lower leg compression injuries, where the mass of your body is driven into the solid brake pedal by the decceleration forces., It also allows the front of your car to rise, meaning your crumple structure will not be as likely to be overridden by the thing you hit! Like i say, hope you never need this one........
Disagree about clutch going down. Brake before clutch (BBC) is a massive help due to additional engine braking effect. This effect is proportionate to the gear, so BBC is still effective at higher speeds(/gear) too, but less pronounced than in lower gears. When clutch goes down with brake, even from 30 mph, it adds at least a metre to stopping distance. BBC is more efficient for ALL drivers, especially as most do not press the brake anywhere near hard enough.
I'm sorry that is simply not true when talking about an emergency stop, ie shortest possible stopping distance. A modern car has a braking system powerful enough (if you press the pedal hard enough...) to be able to reach "fully developed threshold braking" (ie the point at which the wheel/tyre starts to decelerate faster than the car) at any speed. Leaving the clutch engaged means that not only does the engine itself also now have to be slowed by the braking system, critically, the engines inertia, (referenced to the braking wheels by the gear selected) also has to be included in the mass which is under constant decel/accel within the antilock braking systems control loop, as it tries to keep the wheel decel rate just in front of the cars decel rate. As i mentioned, the slipper the road, the more it matters. On a dry tarmac stop (with a pre-adapted ABS controller) we are talking about a couple of percent, but on a wet road, perhaps 5% and on a ice road, as much as 25%.....
In teaching this to learner drivers, I know you are wrong. Obviously, if the clutch stays up too long, the effect you mention is a factor. However, in extremis, the delay in getting clutch down is a BIG help due to engine braking, but it only stays up for probably half a second or so, even less from lower speeds. Also, BBC is a technique that better suits most drivers, most of the time. Have you tried different methods with any students?
i'm not talking about learner drivers, or people learning to brake. I'm talking about stopping a car in the absolutely shortest possible distance! But for a learner driver, the only thing that matters, the only thing that makes any significant difference is to ensure they mash the middle pedal to the floor as fast and as hard as they can, and to keep it mashed!
Great video once again! After years of only owning old cars and now being in a new BMW, I was completely unaware that its possible to emergency brake (a modern car) mid corner and still maintain control. Thats a big takeaway point for me. Cheers!
Excellent video, the 30 mph emergency stop demo clearly puts into perspective how the thinking/stopping distances stated in the highway code can be improved on. I hope to try out the technique soon.
Thank you!! I never knew about the hazards coming on themselves. I was also taught many years ago to pump brakes but now I understand that with ABS it’s different.
I was lucky enough to recently spend a day playing, I mean undergoing vigorous training for work, on a skid pan. The thing that struck me most was the stability during split-mu braking - straight and true with two wheels on a high-friction textured surface and the other on wet polished cobbles. Also, the stability during brake-avoid on the wet cobbles, just a hint of countersteering required to settle a fairly weighty saloon with all its weight being thrown at the front axle. Brilliant feat of engineering and undoubtedly saving lives daily.
A very useful addition to your excellent and informative videos. Reaction time is probably still the biggest variable along with the number of passengers and luggage.
Great even surface ABS video enriched by expert comment. It would be an interesting demo with ABS on uneven surfaces, such as right-hand tyres on bitumen and left-hand tyres on soft shoulder. Without ESC the driver has to fight the car's urge to spin clockwise. ESC trades off some ABS performance for keeping the car pointing where it's aimed.
I've just caught up with all your videos and your driving skills are amazing. I'm just about to take ownership of a M140i and I plan to take a 3 day performance car driving course, its a start but a long off your driving ability. Keep the videos coming!
Great video, Reg! Enjoyed watching! Very useful indeed! Thank you! As a suggestion to add footage from GoPro camera attached to the side of the car, so that the wheels become visible while braking. May be next time. :)
Part of the reason i don't think they will change the braking distances in the highway code is because many drivers thinking distances are SO long, caused by distraction, lack or awareness or poor concentration. At 30mph if it takes someone 1 second to think they need to emergency brake they will have travelled 45 feet
Also braking distances are exponential, as all the main stopping is done in the last few feet before you stop, so going at 35mph will take a LOT long than stopping at 30mph, equally stopping at 40mph takes a LOT longer than 35mph.
sorry Reg, but you're an expert driver with a boss motor, braking to a known point of the brolly. Plus not everyone has a modern car. What about cadence braking? The other day, I braked for bicycle rider ( not cyclist) entering the field of vision from a crossing from the left, had to full stop before he hi my front left corner, no traffic behind, but he gave me a mouthful , didn't thank me, quite the opposite
Something's gone a little bit wrong in the test. Let's say that's a 1.5 car length ~23ft braking distance. From 30mph this gives an average deceleration of about 1.2 x gravity. That's flatout impossible in a vaguely normal road car such as the M135i. It's way past what the rubber-tarmac frictional interface could withstand, unless you had about 700lbs worth of downforce. Generally good rubber/tarmac can give you about 0.9 x gravity. That said, you only need have been travelling about 4mph less for the calculation to give 0.9g. Given how much modern speedos over-read, this is the most likely explanation. A *one* car length braking distance from 30mph is well into the realms of SciFi/Formula 1. You'd need 2g deceleration, which would require down force greater than the weight of the car!. Still a great demo. The 60mph demo was seriously impressive! -A Physics nerd who enjoys your content and is hoping to do some advanced training sometime soon :)
1.2 g under fully developed threshold braking is exactly what you would expect for a reasonably well controlled modern car, on "sports" tyres (high silica content) on a decent, clean, dry tarmac surface! Proper sporting stuff (modern supercar) with the assistance of downforce at high speed, and very sporty tyres ( like the typical "CORSA" tyres etc) can actually get up as high as 1.5g for short periods. Remember tyres are not pure frictional devices, and a large proportion of their grip comes from the mechanical interlocking of the soft rubber tread with the "jagged" road surface. This also explains why tyre grip initially rises against slip percentage (more edges get driven into the surface) and then falls as too much slip occurs (at high slip, there is simply no time for the tyre to conform to the macro texture of road surface). If you think of tyres like velcro, you'll get an idea of how they work ;-)
Max Torque Interesting, that does seem to be backed up by at least one piece of research. In an inexpensive car on inexpensive tyres on a questionable road surface, I wouldn't want to count on more than 0.8g or so. But thanks for the heads up that 1.2g is actually possible under some conditions. I still wonder of Speedo over-reading played a small part here.
Great video, It's amazing (and somewhat scary) just how many drivers how no idea how to stop a modern car and have never actually tried to do so! If i may, i'd add three additional points:
1) LOOK WHERE YOU WANT TO GO!! Really, really, really important, and really, really, really hard to do in a true emergency, where naturally you'll look at the thing you are trying to miss! But, you need to look around it! Many people simply brake, fail to steer and pretty much drive into the object in their way, despite there often being an entirely clear carriageway giving an easy path around said obstruction. The only way to learn this is to practice it ime.
2) Much less important, but in a front wheel drive car, and especially if it's slippy under tyre, you will stop in a significantly shorter distance and with better steering control if you put the clutch in immediately you commence the emergency braking. It's not crucial, it's a more advanced technique, and often gets forgotten, but decoupling the engines inertia (referenced to the front wheels by the gear you are using) from the braking event will allow the ABS to operate faster and more efficiently. In the worst case, in snow or ice, the difference in stopping distance can be measured in 10's of meters!
3) Hopefully you'll never need this one, and if you do, most people won't have time or the ability to carry it out, but if you are in the middle of an real emergency braking event but realise you are NOT going to stop, and are going to hit a large solid object at speed, then it's better to get off the brake (And clutch) pedal at the last possible second to avoid lower leg compression injuries, where the mass of your body is driven into the solid brake pedal by the decceleration forces., It also allows the front of your car to rise, meaning your crumple structure will not be as likely to be overridden by the thing you hit! Like i say, hope you never need this one........
Max, as always, your contributions are extremely helpful, detailed & interesting. Thank you!
Disagree about clutch going down. Brake before clutch (BBC) is a massive help due to additional engine braking effect. This effect is proportionate to the gear, so BBC is still effective at higher speeds(/gear) too, but less pronounced than in lower gears. When clutch goes down with brake, even from 30 mph, it adds at least a metre to stopping distance. BBC is more efficient for ALL drivers, especially as most do not press the brake anywhere near hard enough.
I'm sorry that is simply not true when talking about an emergency stop, ie shortest possible stopping distance. A modern car has a braking system powerful enough (if you press the pedal hard enough...) to be able to reach "fully developed threshold braking" (ie the point at which the wheel/tyre starts to decelerate faster than the car) at any speed. Leaving the clutch engaged means that not only does the engine itself also now have to be slowed by the braking system, critically, the engines inertia, (referenced to the braking wheels by the gear selected) also has to be included in the mass which is under constant decel/accel within the antilock braking systems control loop, as it tries to keep the wheel decel rate just in front of the cars decel rate. As i mentioned, the slipper the road, the more it matters. On a dry tarmac stop (with a pre-adapted ABS controller) we are talking about a couple of percent, but on a wet road, perhaps 5% and on a ice road, as much as 25%.....
In teaching this to learner drivers, I know you are wrong. Obviously, if the clutch stays up too long, the effect you mention is a factor. However, in extremis, the delay in getting clutch down is a BIG help due to engine braking, but it only stays up for probably half a second or so, even less from lower speeds. Also, BBC is a technique that better suits most drivers, most of the time. Have you tried different methods with any students?
i'm not talking about learner drivers, or people learning to brake. I'm talking about stopping a car in the absolutely shortest possible distance! But for a learner driver, the only thing that matters, the only thing that makes any significant difference is to ensure they mash the middle pedal to the floor as fast and as hard as they can, and to keep it mashed!
Great video once again! After years of only owning old cars and now being in a new BMW, I was completely unaware that its possible to emergency brake (a modern car) mid corner and still maintain control. Thats a big takeaway point for me.
Cheers!
Same here. I am an IAM member and I didn't know this too. I thought the car may go sideways at say 40 mph on a wet road.
Excellent video, the 30 mph emergency stop demo clearly puts into perspective how the thinking/stopping distances stated in the highway code can be improved on. I hope to try out the technique soon.
Thank you!! I never knew about the hazards coming on themselves. I was also taught many years ago to pump brakes but now I understand that with ABS it’s different.
I was lucky enough to recently spend a day playing, I mean undergoing vigorous training for work, on a skid pan. The thing that struck me most was the stability during split-mu braking - straight and true with two wheels on a high-friction textured surface and the other on wet polished cobbles. Also, the stability during brake-avoid on the wet cobbles, just a hint of countersteering required to settle a fairly weighty saloon with all its weight being thrown at the front axle. Brilliant feat of engineering and undoubtedly saving lives daily.
Law enforcement training?
A very useful addition to your excellent and informative videos. Reaction time is probably still the biggest variable along with the number of passengers and luggage.
Great even surface ABS video enriched by expert comment.
It would be an interesting demo with ABS on uneven surfaces, such as right-hand tyres on bitumen and left-hand tyres on soft shoulder.
Without ESC the driver has to fight the car's urge to spin clockwise.
ESC trades off some ABS performance for keeping the car pointing where it's aimed.
Hi reg, would be also great to see a sequel to this video doing a motorcycle emergency stop.
Excellent demonstration.
I've just caught up with all your videos and your driving skills are amazing. I'm just about to take ownership of a M140i and I plan to take a 3 day performance car driving course, its a start but a long off your driving ability. Keep the videos coming!
Great video, Reg! Enjoyed watching! Very useful indeed! Thank you! As a suggestion to add footage from GoPro camera attached to the side of the car, so that the wheels become visible while braking. May be next time. :)
Part of the reason i don't think they will change the braking distances in the highway code is because many drivers thinking distances are SO long, caused by distraction, lack or awareness or poor concentration. At 30mph if it takes someone 1 second to think they need to emergency brake they will have travelled 45 feet
Also braking distances are exponential, as all the main stopping is done in the last few feet before you stop, so going at 35mph will take a LOT long than stopping at 30mph, equally stopping at 40mph takes a LOT longer than 35mph.
sorry Reg, but you're an expert driver with a boss motor, braking to a known point of the brolly. Plus not everyone has a modern car.
What about cadence braking?
The other day, I braked for bicycle rider ( not cyclist) entering the field of vision from a crossing from the left, had to full stop before he hi my front left corner, no traffic behind, but he gave me a mouthful , didn't thank me, quite the opposite
Great video Reg. Interesting to see how the car handles corners while excessive braking. Have you ever done this without ABS? Thanks.
Great video but as a Driving instructor the emergency stop happens in 1 in 3 tests so I still teach it up to speeds of 40mph
1 in 8 is the frequency.
take it back - gov. says 1 in 3 but there's no way it's that frequent!
Why not every test?
@john Cookson it is attempted every 1 in 3 it probably actually goes ahead more like 1 in 5
Something's gone a little bit wrong in the test. Let's say that's a 1.5 car length ~23ft braking distance. From 30mph this gives an average deceleration of about 1.2 x gravity. That's flatout impossible in a vaguely normal road car such as the M135i. It's way past what the rubber-tarmac frictional interface could withstand, unless you had about 700lbs worth of downforce. Generally good rubber/tarmac can give you about 0.9 x gravity. That said, you only need have been travelling about 4mph less for the calculation to give 0.9g. Given how much modern speedos over-read, this is the most likely explanation. A *one* car length braking distance from 30mph is well into the realms of SciFi/Formula 1. You'd need 2g deceleration, which would require down force greater than the weight of the car!. Still a great demo. The 60mph demo was seriously impressive!
-A Physics nerd who enjoys your content and is hoping to do some advanced training sometime soon :)
1.2 g under fully developed threshold braking is exactly what you would expect for a reasonably well controlled modern car, on "sports" tyres (high silica content) on a decent, clean, dry tarmac surface! Proper sporting stuff (modern supercar) with the assistance of downforce at high speed, and very sporty tyres ( like the typical "CORSA" tyres etc) can actually get up as high as 1.5g for short periods. Remember tyres are not pure frictional devices, and a large proportion of their grip comes from the mechanical interlocking of the soft rubber tread with the "jagged" road surface. This also explains why tyre grip initially rises against slip percentage (more edges get driven into the surface) and then falls as too much slip occurs (at high slip, there is simply no time for the tyre to conform to the macro texture of road surface). If you think of tyres like velcro, you'll get an idea of how they work ;-)
Max Torque Interesting, that does seem to be backed up by at least one piece of research. In an inexpensive car on inexpensive tyres on a questionable road surface, I wouldn't want to count on more than 0.8g or so. But thanks for the heads up that 1.2g is actually possible under some conditions. I still wonder of Speedo over-reading played a small part here.