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Electric cars & brake lights

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

  1. Tony L

    Tony L Administrator

    This is an interesting/scary video about brake lights on EVs and how they behave in regards to regenerative braking etc. Different manufacturers seem to have wildly different interpretations of the regulations.

    tldr; a lot of EVs are going to get rear-ended.
    sean99 likes this.
  2. sean99

    sean99 pfm Member

    Wow - what an epic fail. The "brake" lights should really be renamed the "I'm slowing down (at a rate exceeding x)" lights and should come on whenever the car slows more rapidly than it would if it could be put into neutral and coast.

    Apparently Nissan had figured this out for the Leaf's one pedal driving mode.
  3. Rug Doc

    Rug Doc pfm Member

    Yeah, let’s reinvent the brake light. What could go wrong.
    Fudgemaster likes this.
  4. Cav

    Cav pfm Member

    Why have a lot of EVs not already been rear-ended?
  5. Tony L

    Tony L Administrator

    I’m sure a lot have. Cars get rear-ended all the time. Brake-lights that don’t indicate rapid deceleration will make that even more likely.
  6. Rodrat

    Rodrat pfm Member

    We have owned EV’s for six years, not one instance of a car behind coming even close to hitting us.
  7. Cav

    Cav pfm Member

    And yet, I have heard of none where the absence of brake lights was a proven cause. In any event, running into the back of another vehicle is usually the fault of the driver of the following vehicle for failing to pay sufficient attention to the road ahead.
  8. Tony L

    Tony L Administrator

    Did you watch the video?
  9. martin clark

    martin clark pinko bodger

    Why? That's not a Thing, at all.

    EVs do not, cannot, decelerate faster than any other kinds of vehicles.

    Brake lights are unchanged as to simply signal 'I am slowing' - since forever. Even the move, to a third, eye level repeater in the early/mid 90s just made such more apparent to the unthinking. That had a small, but barely-detectable, mostly- statistical effect.

    Observation is everything; drivers should be used to no such cues - in fact, that is very important - If you are watching for intensity changes to signal how you should behave in the shoal - it's already far, far too late.

    Side-observation: we are also entering a realm where 'UX-designers' are being put to work, at how drivers might/should drive cars - without any of the experience of doing so!

    A lot of the result, is utterly, utterly ..shit; from a safe-interaction-vs-feedback, vs: diversion-of attention POV: touchscreen-everything, for a start.
  10. Tony L

    Tony L Administrator

    Did you watch the video? The guy demonstrated his Hyundai EV could decelerate from 60 to zero in 13 seconds without the brake lights activating until it was actually stationary!
  11. martin clark

    martin clark pinko bodger

    That's the kind of observation that any driver notices! diminution of space in front, driver ahead isn't maintaining speed uphill etc. Or - car ahead , limiting speed downhill, by selection of lower-gear and using engine-braking (per highway code, road signs etc) -it'll slow at an arbitrary rate, even abruptly - with no external signal.

    13s 60-0 deceleration rate is .. really bloody slow ... a vehicle ahead coasting uphill to a stop without brakes, also , long, perfectly normal; say a motorway off-ramp. You might see a flash in the last second or two as vehicle ahead brought to a positive stop/held.

    TBH - as a driver, one in the shoal - you watch for the relative movement of the Shoal around you, to avoid incursion into the stand-off space you are managing - ahead, to the side, behind. Vehicle signal lights - brake, indicators - are not to be relied-upon, ever.

    If you wait for, let alone believe, signal of intention, you've failed.

    Easier to demonstrate, than discuss - ATB : )
  12. Seeker_UK

    Seeker_UK Feelin' nearly faded as my jeans

    To put that into perspective, that's about 180m of travel before it stops.

    The braking distance for 60mph in the Highway Code is 55m (73m stopping).
  13. Cav

    Cav pfm Member

    You do not drive if I remember correctly?
    awkwardbydesign likes this.
  14. RJohan

    RJohan pfm Member

    I was once rear ended and had neck pains for several years. Long before EV's was around. An idiot behind is an idiot behind.

    But, yeah, I see the problem.
  15. MikeMA

    MikeMA pfm Member

    Tony rides a bike if I remember correctly. You don't need to be a car driver to be a legal road user with a legitimate interest in vehicle lighting and warning systems. If you think otherwise you should seriously consider giving up driving.

    Any how, I think the guy in the video has a point. While brake lights are just one of the many visual clues as to what may be happening on the road in front of us, they are important nonetheless.
  16. matt j

    matt j pfm Member

    I give everyone more room than they need regardless of the vehicle because most people can't drive for toffee, even more so these days when they're doing twelve more important things than actually watching the road.
  17. George J

    George J Herefordshire member

    I would think that it would be relatively easy for a signal to be sent [via the computer] to the brake light circuit from any regeneration that is effectively braking. It would not require any special software to decide the amount of braking, but rather that regenerative braking is occurring.

    When I was taught driving before my third driving test [two fails!] in 1979, I was told to dab the brakes as soon as I had changed down a gear for engine braking going downhill or approaching a junction for examples, as this gives the driver behind an indication that I am restricting the speed by means that would otherwise not be obvious from the braking lights.

    Nowadays it may be too much to hope that this will be done by many drivers, given that so many seem to think that even turn signals are optional, but it could so easily be done on EVs to illuminate the braking lights whenever regeneration is working.

    Best wishes from George
    sean99, Steve 57 and RJohan like this.
  18. simon g

    simon g Older, wiser but no longer retired

    I drive a car with regenerative braking. The brake lights come on if the brake pedal is pressed, or when the regen system braking exceeds a certain force.

    Having brake lights come on whenever regen is active would be extremely problematic, as they would become a distraction to other road users. Driving a car with full regen does require some acclimatisation.

    The best way to avoid rear ending is to pay proper attention to the road and not be distracted by phones, sat nav settings, radio, music, etc etc.
    PrettyVacant and RJohan like this.
  19. PeteVid

    PeteVid pfm Member

    I have an EV and only seldom use the brakes, I use the regenerative braking by taking my foot off the accelerator. To do this you have to use a longer ‘braking distance’ ie start to slow down sooner before you need to stop, hence the deceleration is over a longer period and more gentle which I think reduces the chance of being rear ended .
    PrettyVacant likes this.
  20. Tony L

    Tony L Administrator

    The point here is there is a clear difference between the way brake lights work on certain EVs and any other road-legal vehicles. This means under similar fairly rapid deceleration that has always triggered brake lights in the past certain EVs give no indication at all.

    I’d argue as a road user that the braking technology doesn’t matter. No one should care if a given deceleration is via brake pads or regenerative. The lights should behave in a consistent manner as their sole reason for existence is to signal deceleration to vehicles behind.

    To put it even more clearly there is no way of decelerating a petrol or diesel vehicle from 60 to zero in 13 seconds without activating the brake lights short of driving it into a wall. As such if anyone is defending this specific EV behaviour they are arguing for a substantial change to the existing concept and implementation of brake lights on road vehicles. I’ve no idea why anyone would make that argument. The lights are there to show a vehicle is slowing down, and that is exactly what they should do.
    sean99 likes this.

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