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Electric cars & brake lights

Discussion in 'off topic' started by Tony L, May 25, 2023.

  1. hc25036

    hc25036 pfm Member

    On my EV the brake lights are a little too quick to come on when using regenerative braking and my only issue in 2 years has been tailgating idiots who assume I am brake-testing them when I’m simply easing off the accelerator to take a bend or whatever.
  2. RJohan

    RJohan pfm Member

    And they react by creeping even closer?

    When I'm tailgated I slowly crawl down to a halt and let them pass. Then it some one else's neck that will be hurt next time.
  3. Richard Lines

    Richard Lines pfm Member

    Good Morning All,

    As an ex-owner of a Mk.II Jaguar I was always fascinated about the existence of the badge on the rear bumper warning the car was fitted with discs all round - obviously the cars ability to slow was markedly better than it's drum brake forbearers (having said this the split brake lining system on the early Land-Rovers/ Triumph Roadsters were actually quite effective).

    Our Zoe50 automatically operates the brake lights when regeneration is active above 40mph. The level of regeneration available depends on the amount of uncharged battery as I'm sure people will be aware. Thus there is little to no such braking when the battery is full so it is all conventional brake pedal. In the case of the Zoe there are only two levels of regeneration/ braking available and even on the highest mode I find you need to assist it with the brake pedal although the challenge can be judging when to take your foot off the accelerator if you want to 'coast' up to a roundabout and keep rolling (other traffic permitting).


  4. Seeker_UK

    Seeker_UK Feelin' nearly faded as my jeans

    I'm sorry but your POV isn't based on the facts. The brake lights are there to signal that the driver in front has applied the brakes, nothing else.

    "All stop lamps must light up immediately when the brake is applied and switch off immediately when the brake is released".) UK MOT guidance - stop lamps must light,with only 1 stop lamp.

    It is one of several visual clues that road users have that a vehicle is slowing down. As stated elsewhere, a car getting closer to you is another. If you are unable to react in time, then you're reactions are too slow, or you're too close and / or shouldn't be driving.

    In an ICE car, the driver can slow the car by taking their foot off of the accelerator and using engine braking and regeneration (in mild hybrid cars); the effect is no different to the EV slowing down and there is no legal requirement for the brake light to illuminate. That said, BMW and others do illuminate their stop lights when a car slows down under regen / reduction in cruise speed but that is manufacturer's going above the legal requirement for safety sake. See also flashing brake lights under hard braking.
    Sue Pertwee-Tyr likes this.
  5. Sue Pertwee-Tyr

    Sue Pertwee-Tyr neither here nor there

    I don't think this is correct. 60-0 in 13 seconds is pretty mild deceleration, very similar to what you could achieve under engine braking in an ICE car, a situation which similarly doesn't illuminate the brake lights.

    I once followed a guy in a Caterham Seven, and his brake lights never came on, despite some decelerations which had me applying the brake in my car. I called out to him when we got to some lights, to warn him that his brake lights were faulty (it was a kit car, so this was not an unreasonable assumption). He laughed and said he hadn't been using his brakes, because the engine braking was so effective he seldom needed to.
  6. Tony L

    Tony L Administrator

    To my interpretation your statement below and the passage you quote backs my point fully:

    The brake lights are there to signal that the driver in front has applied the brakes.

    "All stop lamps must light up immediately when the brake is applied and switch off immediately when the brake is released".)”

    You seem to be viewing the term ‘brakes’ as a 20th century friction-based concept such as drums or discs. You are describing a specific device, not a concept or behave. From a logical perspective the term should include all technology that behaves in a way that applies rapid controlled deceleration in that manner. The driver in the vehicle behind shouldn’t need to make allowances for different technologies. There should be no “oh, that’s an EV, best assume it has no brake lights” aspect to this. On a rainy foggy morning up on the moors these things matter.

    A modern EV brake light should indicate deceleration of the kind that would occur in old 20th century petrol/diesel vehicle technology were the brakes to be applied. The visual indicators should be entirely consistent with deceleration behaviour of the vehicle, the technology is irrelevant.
  7. Seeker_UK

    Seeker_UK Feelin' nearly faded as my jeans

    It's not my "view". I'm quoting the law.

    Just to clarify one thing, the deceleration you cite is SLOW, and something that you will see with ICE cars and no-one has posted a video about that.

    If the laws need to change, there needs to be a strong body of evidence that the rules that exist for ICE cars are causing more collisions, in particular life changing or fatal ones, with EV cars. One youtuber and one forum owner saying there's a problem isn't a sufficient evidence base required to do so. At the very least, EV manufacturers should implement brake lights under regen (as they do for some ICE cars)

    You are also conveniently ignoring my other comment that it is really bad driving if you only depend on brake lights for visual clues on other road user's behaviour.
    lordsummit and Big Tabs like this.
  8. Konteebos

    Konteebos Surfing on the lake of fire

    Tesla brake lights come on with regenerative braking, possibly a little too early but that's much better than not at all. I don't use the brake pedal much in normal driving.
  9. Vinny

    Vinny pfm Member

    Endless designs on combustion engine vehicles have insanely poorly placed/small brake lights anyway.

    I was in slow-moving traffic two days ago, in broad daylight, and either it was part of the design or the driver in front chose to have their lights on. The brake light was so slim and the rear lights were a series of same-sized red lights, it was all but impossible to be certain that brake lights came on - and that was from 20-30 feet away, at a guess. We weren't going at any significant speed..............

    Essentially the same appears on endless current cars. The same goes for indicators - endless front ones are too close to the headlights and far too small to be seen after dark.
  10. Tony L

    Tony L Administrator

    The video indicated falling off the parcel shelf and IIRC stated a force of 3g. I’ve no idea why some drivers here view this as controversial.

    I never ignore bad driving. I’ve very nearly been killed by it multiple times. As a cyclist I’m very frequently overtaken just prior to a left turn where the motorist then immediately they are in front slams the brakes on forcing me to brake/swerve in a really dangerous manner. Plus huge numbers of drivers around here are pissed or stoned (often a real stink of skunk at lights etc). Please don’t take away the few remaining visual cues!

    PS To be honest I’ve all but given up road cycling now. Just way too many pricks out there. They’ve effectively driven me off the road to the extent the £4k titanium road bike in the hallway only has a few hundred miles on it. I stick to canal paths on the old school MTB now. Just way, way safer.
  11. hc25036

    hc25036 pfm Member

    We live out of town with windy country roads. Morons drive too close in the hope that the next bend will open out into a mile of open road so they can scream past in their 15 year old Peugeot….
    RJohan likes this.
  12. Seeker_UK

    Seeker_UK Feelin' nearly faded as my jeans

    He meant 0.3g. Deceleration of 3g means stopping in under 1s from 60mph. :eek:

    The deceleration he demonstrates is very very slow and nothing different compared to current ICE vehicles and people are not being killed in vast numbers in 'rear-enders'.

    It's a bit of a non-story. Maybe he's running out of 70s and 80s electronic doodads to talk about to keep his viewer numbers up. ;)
  13. Sue Pertwee-Tyr

    Sue Pertwee-Tyr neither here nor there

    Agree with this. Emergency braking would probably stop most cars from 60mph in about 3 seconds, so about 1g, maybe a little better in good road conditions, good tyres, etc. Sharp braking, ie the sort that could take a following driver by surprise, might be half that, so 6s 60-0. I'd say gentle braking would achieve the same in perhaps 10 seconds, and a following vehicle would only really have a problem if not paying sufficient attention, or if tailgating really close. So 60-0 in 13 seconds is a pretty gentle drift down to a standstill, very much akin to taking your foot off the gas in, say, next to top gear and letting the car decelerate under engine braking. Nobody expects or requires brake lights to activate for that. It's what I do when approaching a junction and I can see that I'll have to stop. Not <touches wood> been rear-ended yet for that.
  14. awkwardbydesign

    awkwardbydesign Officially Awesome

    And that is exactly what brakes are. Not engine braking or deceleration. Your interpretation is faulty.
    Cav likes this.
  15. Tony L

    Tony L Administrator

    That’s certainly what they were in the fossil fuel-era. The fact brake light legislation is already changing in the EU (see end of video) suggests there is rather more to it with new technology. Again I’m surprised how many people are digging-in against something that would obviously make road use safer.
  16. Sue Pertwee-Tyr

    Sue Pertwee-Tyr neither here nor there

    I'm not digging in, but (while I haven't watched all the video) I don't think what I saw, and what you have reported, makes the case for change.
    Cav likes this.
  17. awkwardbydesign

    awkwardbydesign Officially Awesome

    Again, your interpretation is wrong. Nothing to do with digging in, simply understanding what the term means in law. And if you read the posts here, it wouldn't necessarily make road use safer. If you drove you might understand it better.
    Until very recently I rode a twin cylinder motorbike, and rarely had to use the brakes. But I did if I needed to warn someone behind me.
    Cav likes this.
  18. Sue Pertwee-Tyr

    Sue Pertwee-Tyr neither here nor there

    How often would you say brake lights coming on has been your first indication that something was about to happen?
  19. sean99

    sean99 pfm Member

    I'm with Tony on this. I used to work on driver behavior monitoring using accelerometers and CAN bus data. 0.3G is more than a gentle coast to a stop. An emergency stop on a dry road with ABS in a typical family car is around 0.75G. Taking my foot off the gas in my automatic ICE car would result in a deceleration of no more than 0.1G.

    Clearly, where regenerative braking and one pedal driving can slow the car more rapidly than coasting in an ICE car there's a balance to be struck as to when the vehicle puts on the brake lights - it can no longer simply be a function of the brake pedal being pressed - it has to be based on deceleration above a certain threshold. It seems like Hyundai have set that threshold a little too high, and it sounds like Tesla may have set that threshold a little too low, judging by reports that Tesla brake lights come on perhaps a little more than they should.

    Of course following drivers should pay attention and not rely on brake lights alone, but the video does suggest that Hyundai might want to think about a software update to enable the brake lights a little sooner.
  20. Sue Pertwee-Tyr

    Sue Pertwee-Tyr neither here nor there

    Thanks for that, and you make a good point. However 60-0 in 13 seconds is a little under 0.25g, not 0.3g, and an ICE car in anything other than top gear will likely decelerate much more under engine braking than an automatic will, so I'd not be surprised to see something approaching 0.2g under engine braking in some circumstances.

    That said, I tend to agree with your conclusion - looks like Hyundai may have undercooked it; we probably need some form of certification standard to get a degree of uniformity and predictability.
    sean99 likes this.

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