Electric vehicle queries

[raybarrow]

Hi,

If you find it necessary to tailgate, remind me not to drive in front of you. Or better still, you can go by train

Tongue in cheek obviously. Never understood the mentallity of tailgating. When/if the HS2 finally appears, maybe not in my lifetime, and they increase the capacity of trains, there may be some high speed tailgating going on. No, I'm sure it will be very safe - won't it?
Ray.

[kempiejon]

Hi,

If you find it necessary to tailgate, remind me not to drive in front of you. Or better still, you can go by train

Tongue in cheek obviously. Never understood the mentallity of tailgating. When/if the HS2 finally appears, maybe not in my lifetime, and they increase the capacity of trains, there may be some high speed tailgating going on. No, I'm sure it will be very safe - won't it?
Ray.

Come the AI driving revolution there'll just be strings of car trains on the roads with the vehicles peeling off or slotting in. It would improve the flow through traffic lights no end rather than each car waiting for the car in front to notice it's their turn to move.

[Mike4]

Engineering wise IC engines can only run in one direction.

Point of Order M'Lud...

This is not universally true of IC engines.

The 7 litre, two-stroke hot bulb semi-diesel IC engine I had in by boat for a few years could run in either direction. But a problem with lubrication when running backwards meant it needed stopping and restarting on the occasions it ran backwards.

And on the Bolinder engines in historic narrow boats, there was no reversing gearbox. The driver ('steerer' to use the correct terminology) would skilfully stop the engine in such a manner it instantly re-started in the opposite direction for 'braking' when the boat needed to stop.

[staffordian]

Engineering wise IC engines can only run in one direction.

Point of Order M'Lud...

This is not universally true of IC engines.

The 7 litre, two-stroke hot bulb semi-diesel IC engine I had in by boat for a few years could run in either direction. But a problem with lubrication when running backwards meant it needed stopping and restarting on the occasions it ran backwards.

And on the Bolinder engines in historic narrow boats, there was no reversing gearbox. The driver ('steerer' to use the correct terminology) would skilfully stop the engine in such a manner it instantly re-started in the opposite direction for 'braking' when the boat needed to stop.

And what about the Messerschmitt car?

To reverse, stop the engine, switch the contract breakers and restart the engine. All four forward gears then available for reversing.

https://en.m.wikipedia.org/wiki/Messerschmitt_KR200

[Niksen]

I was driving behind an electric Hyundai yesterday and his brake lights kept coming on for just a second as though he/she was just tapping the brakes, not noticebly slowing down. No queue of traffic and not hitting the speed limit. I drive a petrol auto and on downhill bits sometimes have to do this but this was a flat road. Could regenerative braking cause that or is regen braking just like dropping down a gear and letting the engine slow you down?

Regenerative breaking will trigger the brake lights if the the result of that regeneration is sufficient deceleration - Kia/Hyundai in the US had to roll out a software upgrade to their cars there last year to reduce the threshold of deceleration before the lights activated because the threshold was considered too high and it increased the risk of a rear end accident.

With most EVs there is an option of the level of regenerative braking or even automatic regenerative braking using the car's forward radar system.

An awful lot of people with EVs choose the maximum regeneration because it gives them a 'one pedal' style of driving, frequently referred to by the EV geeks as 'iPedal', because then they can just effectively use the accelerator to drive.

With the car you saw with the brake lights coming on and off on a flat road with no traffic, then it might have been someone who had the car set at that maximum regeneration and that regeneration was caused by them lifting off the accelerator for no reason, or they might just have been an old fashioned accelerate / brake driver of the type who can't sit at a steady speed whatever they are driving.

[9873210]

Regenerative breaking will trigger the brake lights if the the result of that regeneration is sufficient deceleration

This is not a regenerative braking issue. It's a drive by wire or control issue.

What matters is that the car is slowing, not how it is slowing.

With drive by wire and an automatic you can make an ICE car drive exactly the same as an EV. Single pedal driving and aggressive slowing if you lift off the accelerator are software controlled and have little to do with the motive power.

EVs can stop using plugging, which is not regenerative. Doesn't matter, brake lights should still come on.

The rules should also require a manual ICE vehicle to detect aggressive engine braking and use the brake light.

[Niksen]

What matters is that the car is slowing, not how it is slowing.

Of course that is the case, but with cars other than EVs it is pretty hard to make them slow rapidly enough to need the brake lights coming on without pressing the brake pedal.

[9873210]

What matters is that the car is slowing, not how it is slowing.

Of course that is the case, but with cars other than EVs it is pretty hard to make them slow rapidly enough to need the brake lights coming on without pressing the brake pedal.

It's not hard to slow without pushing the brake pedal. On any car with ABS or traction control (let alone automatic emergency braking) the hardware must allow a pretty rapid stop without any driver input, let alone the brake pedal being pushed. These features are common (sometimes mandatory) on modern cars. Software has been able to override any direct link between the brake pedal and the brakes for quite a while. The vehicle design specs need to say when the brake lights go on, and barring unreliable Heath Robinson interlocks this means the brake light control ends up in the software specs.

Modern cars are a lot closer to drive by wire than most people imagine.

[Lootman]

Software has been able to override any direct link between the brake pedal and the brakes for quite a while. The vehicle design specs need to say when the brake lights go on, and barring unreliable Heath Robinson interlocks this means the brake light control ends up in the software specs.

Modern cars are a lot closer to drive by wire than most people imagine.

And therein lies the problem. Just ask the family of anyone who died in a 737-MAX plane or of that woman in Arizona who was run over and killed by a self-driving EV on a pedestrian crossing.

There should always be an override capability. One of many reasons why I drive a 20 year old car.

[9873210]

And therein lies the problem. Just ask the family of anyone who died in a 737-MAX plane or of that woman in Arizona who was run over and killed by a self-driving EV on a pedestrian crossing.

There should always be an override capability. One of many reasons why I drive a 20 year old car.

Brake lights have never had an override capability, unless you count reaching under the dash and yanking wires.

The 737-MAX did have an override capability. The pilots were not trained in it, did not understand it, and (arguably) could not understand it in the context of available training and the crashes. But had they been briefed on exactly what was going to happen before the flight they would have landed safely.

The Uber had a safety driver with full override control. This did not do any good.

If you have a man-in-the-loop the trick is to have the automate systems behave consistently in a manner the a) humans are capable of understanding b) The humans involve actually understand and c) are compatible with human behaviour. Arbitrary requirements for overrides are hot air and exist so somebody can blame the pilots for systemic errors.

[Lootman]

And therein lies the problem. Just ask the family of anyone who died in a 737-MAX plane or of that woman in Arizona who was run over and killed by a self-driving EV on a pedestrian crossing.

There should always be an override capability. One of many reasons why I drive a 20 year old car.

Brake lights have never had an override capability, unless you count reaching under the dash and yanking wires.

The 737-MAX did have an override capability. The pilots were not trained in it, did not understand it, and (arguably) could not understand it in the context of available training and the crashes. But had they been briefed on exactly what was going to happen before the flight they would have landed safely.

The Uber had a safety driver with full override control. This did not do any good.

If you have a man-in-the-loop the trick is to have the automate systems behave consistently in a manner the a) humans are capable of understanding b) The humans involve actually understand and c) are compatible with human behaviour. Arbitrary requirements for overrides are hot air and exist so somebody can blame the pilots for systemic errors.

All that is fine but again I still have to be able to switch off HAL. Just in case HAL goes insane.

[Hallucigenia]

All that is fine but again I still have to be able to switch off HAL. Just in case HAL goes insane.

"goes" ?

[Niksen]

Of course that is the case, but with cars other than EVs it is pretty hard to make them slow rapidly enough to need the brake lights coming on without pressing the brake pedal.

It's not hard to slow without pushing the brake pedal. On any car with ABS or traction control (let alone automatic emergency braking) the hardware must allow a pretty rapid stop without any driver input, let alone the brake pedal being pushed.

Sure they slow, but do they slow enough to warrant the brake lights activating.

The regulations for the brake lights coming on for regeneration are that they must not come on if the deceleration is less than 0.7m/s squared.

It is up to the manufacturer if they come on between 0.7 and 1.3, but they are only required to come on if the deceleration is more than 1.3m/s squared but must turn off when the deceleration falls below 0.7.

I think it doubtful that ABS or traction control would slow the car by more than 1.3m/s squared with no brake pedal input, and more likely the deceleration is below the 0.7 level where brake lights must not be illuminated.

[servodude]

It's not hard to slow without pushing the brake pedal. On any car with ABS or traction control (let alone automatic emergency braking) the hardware must allow a pretty rapid stop without any driver input, let alone the brake pedal being pushed.

Sure they slow, but do they slow enough to warrant the brake lights activating.

The regulations for the brake lights coming on for regeneration are that they must not come on if the deceleration is less than 0.7m/s squared.

It is up to the manufacturer if they come on between 0.7 and 1.3, but they are only required to come on if the deceleration is more than 1.3m/s squared but must turn off when the deceleration falls below 0.7.

I think it doubtful that ABS or traction control would slow the car by more than 1.3m/s squared with no brake pedal input, and more likely the deceleration is below the 0.7 level where brake lights must not be illuminated.

Honestly I'd be more worried about what automatic lights, based on measured changes in speed, did when stationary

[Arborbridge]

This is all quite interesting. In the old days, just activating the pedal would bring on the brake light whether the car slowed or not. Now, the brake light can come on whether you press the pedal or not, in theory.

Reacting to the deceleration of the car seems more rational, provided the system can react fast enough.

Arb.

[DrFfybes]

Honestly I'd be more worried about what automatic lights, based on measured changes in speed, did when stationary

Nothing, unless you press the pedal.

However some brands now allow you to set them so the brake lights come on when you are stopped on the 'handbrake', which means you can dazzle the driver sat behind you at the lights at night without even having to press the pedal. However only the truly inconsiderate would think that was acceptable.

[bungeejumper]

This is all quite interesting. In the old days, just activating the pedal would bring on the brake light whether the car slowed or not. Now, the brake light can come on whether you press the pedal or not, in theory.

In the old days, a brake light was a hazard warning which it would be very foolish not to take seriously. And the best way to start a multi-vehicle pile-up on a busy motorway was for some twerp to brake when he didn't really need to.

Let's call his braking force X. So the car behind him sees his brake lights and brakes with force X, plus a bit, because he doesn't know yet what has prompted driver 1 to do this. Better safe than sorry.

The car behind him sees his brake lights and brakes a bit harder than him, and the guy behind him does the same thing. Six cars back in the queue, the required braking force has at least doubled, and the likelihood of a proper carambolage is becoming more real by the second. It happened to a friend who was number ten in a sixteen vehicle shunt on the M4. A good job (for him) that he was driving a Volvo estate and not a shopping car.

The point is, each driver is behaving quite rationally to an unknown and unexplained situation in front of him. Yes, we could certainly object that everyone should be driving within his stopping distance down to zero, but when was the last time you actually saw that happening on a motorway? The gaps between cars would be so large that the road's traffic capacity would be massively reduced.

I'm not saying that nobody is at fault here - just that human nature is the way it is. Brake lights coming on just because somebody is no longer actively accelerating is something that we'll all have to get used to, I suppose?

Okay, fire away.

BJ

[Niksen]

However some brands now allow you to set them so the brake lights come on when you are stopped on the 'handbrake'

I am not sure any manufacturer offers the ability to allow the driver to set that.

My experience is the car simply illuminates the brake lights whilst the car is stopped with 'auto-hold' operative and there is no setting to disable that occurring. I suppose theoretically you could manually engage the parking brake, but in some cars I have used that automatically moves the car from 'Drive' to 'Park' because you have engaged the parking brake, so I can't see many drivers doing that at the traffic lights.

[staffordian]

However some brands now allow you to set them so the brake lights come on when you are stopped on the 'handbrake'

I am not sure any manufacturer offers the ability to allow the driver to set that.

My experience is the car simply illuminates the brake lights whilst the car is stopped with 'auto-hold' operative and there is no setting to disable that occurring. I suppose theoretically you could manually engage the parking brake, but in some cars I have used that automatically moves the car from 'Drive' to 'Park' because you have engaged the parking brake, so I can't see many drivers doing that at the traffic lights.

I now have my first car with an electronic handbrake and a separate auto hold. It has manual transmission. Pressing the auto hold means that when the car has come to a halt having used the brakes, the hydraulic brakes, not the handbrake, are kept on, with the three rear brake light illuminated. The brakes automatically disengage when the clutch and accelerator are depressed, and despite my initial scepticism, it works well, and hill starts are no problem.

However I would not use this at night, if a driver is following me because it would dazzle them. Not many others seem to worry about that though. The alternative is to use the electronic handbrake, but this is more hassle than with a conventional handbrake. To activate it or release it, the brake pedal has to be pressed at the same time; hardly a major problem, but one more safety feature which adds complexity, and of course, it illuminates the rear brake lights as you are about to move off, which might confuse the following driver.

And so far, I have not worked out how to release the handbrake without starting the car. My drive is on a slope, and I park against the garage door (unfortunately the garage is too small for the car, but thats another story). If I want to open the boot, I used to get in the car, depress the clutch and ease off the handbrake to allow the car to roll forward a few feet. Can't do that with an electronic handbrake, as far as I can tell.

[Howard]

Brake lights coming on just because somebody is no longer actively accelerating is something that we'll all have to get used to, I suppose?

Okay, fire away.

BJ

I have driven many BEVs over the past few years and none of them illuminated their brake lights when "no longer actively accelerating". The lights only came on when they were braking. The braking force came from either the physical brakes or the engine braking. On the flat this meant the car was slowing down, going down hill it meant the driver was keeping the car under control.

Nothing much has changed in car braking. However I often follow ICE cars whose brake lights come on frequently because the driver is nervous or just keeps touching the brake pedal.

regards

Howard