I hate how regen turns on the brake lights. I bet it makes everyone behind me think I'm brake checking them. Very dangerous IMO. Brake lights should come on only when I touch the brake. Regen feels to me equivalent to downshifting in a car to slow down, but brake lights do not engage when downshifting....and they should not engage for regen braking either. I want an option to turn this off please!!
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Regen and Brake Lights - Highway Issue
- Thread starter Zas
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- Driving Dynamics Model S
The CHMSL must "burn steady" and may not flash (there have been many denials, and only one exception was granted to Mercedes-Benz to study the effects of flashing). The regulation was written many years ago and pre-dates many-element lamps, like LED's, so there is no provision for using it as a strength indicator (in the most restrictive sense, "burn steady" would mean all-or-nothing). I suppose Tesla could apply for an exception to do a deceleration strength indicator, but then you'd have to get the general public to understand that it represented deceleration strength vs. being a cute KITT-in-the-rear-window lookalike that will just distract them more.
I am not one of those drivers that sees the brake pedal as a binary condition. When I lived in a different state than the one I live now, I saw plenty of them, though -- brake light in front of you on US 101 meant "slam on your own brakes" apparently in driving school.
To change the behavior of the CHMSL to leverage the new capability in LED strips, you'd probably have to get a few manufacturers together to agree upon it and jointly speak to the NHSTA.
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I sincerely think this won't happen.
Brake lights not lighting on a downshift are the result of decades-long lack of capability (no computers to determine deceleration), combined with a diminishing presence of manual cars and the fact that aggressive downshifting to slow is not a normal operation. Couple this with an engine noise indication - the Jake brake / deceleration can typically be heard. The safety of a notice that the car is decelerating more than expected (vs. coasting) is going to trump anything else. Unless it's shown that it causes more accidents than prevents (a pretty tall order) you won't see it changing any time soon. The 30 kW @ highway speeds threshold seems smart to me and in practice would be the line I would choose for having them come on vs. stay off.
Here's what I do.... I get the braking done before I pass them... once I past the cop I get back on the "gas" and float the petal so that it's truly coasting.
I don't like low regen because I do want full regen sometimes. maybe an adaptive low mode where if you slightly take the brake petal (without actually breaking at all) will slowup ramp up the regen from low to normal... that would be a good idea... but then I'd be taping the brakes all the time.... there's not ideal setup unfortunately
Personally I think the braking 'logic' is near perfect. I spend maybe a little too much time looking at the graphics every now and then to see when the lights are coming on (it's easy at night, as you can see it in the rear view camera). 95%+ of the time, they're reacting exactly as I would expect and require, and I am one of those people that believes there's absolutely no need to brake on a freeway 80% of the time, too many people are dabbing brakes because they're fiddling with their phone or whatever, which just causes a brake ripple through the traffic, partly because many drivers like to drive 10ft off the car in front (in Texas, at least...where I'm from everyone was taught the '3 second rule', and most people adhered to it). Good thing many of those cars are not pieces of crap that couldn't stop quickly without hitting a wall :-/
As an aside, back in the day I had a Vauxhall Astra GTE, which had a LCD dash (v modern at the time), and a serious of 'check lights', one of which was for the brakes, and wouldn't extinguish until it saw the brake bulbs light up. I once made it from my house to office without braking, which was about 15 miles, with lots of roundabouts and lights. I felt good about it at the time
As an aside, back in the day I had a Vauxhall Astra GTE, which had a LCD dash (v modern at the time), and a serious of 'check lights', one of which was for the brakes, and wouldn't extinguish until it saw the brake bulbs light up. I once made it from my house to office without braking, which was about 15 miles, with lots of roundabouts and lights. I felt good about it at the time
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I think the current behaviour is perfect. If regen is slowing down rapidly with no indication to the people behind you (who are often txting or distracted in some other way), your chances of getting rear ended are much higher. And while the Tesla is the safest car on the road, getting hit still does damage to the car, and I'd rather avoid that.
For anyone who hates the bake lights, they can just ease up more gently on the Accelerator so the deceleration is not enough to trigger the lights. It's easy to do.
For anyone who hates the bake lights, they can just ease up more gently on the Accelerator so the deceleration is not enough to trigger the lights. It's easy to do.
I can't stand the accelerometer driven brake lights. I'm used to manual transmission cars and downshifting. The most common scenario for me where this is an issue is passing. When you pass someone, you use a bit of that Tesla torque in order to get past quickly and safely, then let the regen bring your speed back to cruising velocity, but to the driver you passed, this move looks highly aggressive since the brake lights come on as soon as you are back in front of them. If there were an option, I'd turn this off and use my brake pedal to notify other drivers of when I'm *actually* stopping.
After driving a P85 last weekend, I can say that the regen is significant enough that it feels like braking - your body lurches a little bit forward. Given the severity of the regen, brake lights are absolutely required. Just because you can downshift in a stick shift ICE car and apply engine braking without lighting up your brake lights does not make that a safe thing to do, and is hardly a model for other cars. If I were to let up on the pedal of my automatic transmission ICE car, I would have to apply the brake to achieve deceleration equal to what the Model S regen provides, so brake lights are needed. Even when downshifting in a manual transmission ICE vehicle, you run a huge risk of being rear-ended when there is no visual indicator to the person behind you of your change in forward velocity. By the time the driver behind you notices your rear end getting bigger, it may be too late to stop.
Safety first.
Safety first.
I'm not convinced that the brake light is driven by either an accelerometer or the amount of power being generated. It makes more sense to simply measure the deceleration via the wheels (using the same sensor as the speedometer). In my experience, when I drive down a hill at a steady speed, I can generate more that 30kW but the brake lights do not come on, so it's definitely not the amount of power being generated that triggers it.
Brake lights going on for regen is absolutely a safety issue. I think it would be a bad idea to take this away or make it an option to turn it off. If you have ever rode a motorcycle you would know that letting off the throttle decreases your speed a lot, like regen, so you are taught (at least I was taught) in the Motorcycle Safety Foundation classes to tap your brake lever to tell cars that you are slowing down.
The Model S is not a manual car, and whether downshift braking should cause brake lights to come on in a manual car is another issue entirely (ideally I think they should). The brake lights in the Tesla come on at exactly the same times they would in an automatic when people hit the brakes. When I check, I always see the lights coming on whenever I would be hitting the brake in a normal car. They don't come on if I'm just modulating my speed, and they never ever come on when I'm on the freeway, unless I'm slowing rapidly because of traffic in front of me. If traffic has slowed suddenly I can generally slow really quickly using full regen and not use the brake pedal until the last second, and it would be really frightening if the cars behind me didn't see brake lights.
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If you are regen braking quickly enough to cause the brake lights to come on, then in my opinion you are driving highly aggressivly. Gentle regen to bring you back to cruising speed should be sufficient, rather than high regen to quickly slow you down (which, if you are doing, your brake lights should definitely come on).
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If you are regen braking quickly enough to cause the brake lights to come on, then in my opinion you are driving highly aggressivly. Gentle regen to bring you back to cruising speed should be sufficient, rather than high regen to quickly slow you down (which, if you are doing, your brake lights should definitely come on).
mknox
Well-Known Member
While I'm inclined to agree, the reality is that I frequently find myself lifting my foot right off the accelerator when I see brake lights come on in front of me on the freeway, and then quickly getting back on it if traffic isn't actually coming to a screeching halt. This, of course, causes my brake lights to flash. I guess it is an old ICE habit where I would quickly "cover the brake" in case I actually did need to stop in a hurry, and the ICE would tend to coast more than decelerate when you did this. I've had the car 6 months and I'm finding it a hard habit to break. (pardon the pun).
I live in Illinois. We don't have these hill things.
Seriously, I didn't mean to imply it's driven by the amount of power, that's just where it kicks in at highway speeds on flat roads. It may be rate of deceleration as a %age.
strider
Active Member
Did some googling and it's becoming common on European cars:
Peugot: Hazard lights on the move - PistonHeads
Alfa: Hazard Lights When Braking - Alfa Romeo Forum
VW: VWVortex.com - Automatic hazard lights under emergency braking?
A Tesla at full regen slows down MUCH faster than downshifting a car. My last car was a C6 Corvette with a 6.2L V-8 - lots of engine braking available with that motor but my Tesla slows faster. This is an important safety feature IMO and am glad they did it. If you are smooth with the accelerator the lights will not come on unless you are slowing quickly. But if you want to turn this feature off then switch your regen level to low and they won't come on.
I'm not saying they CAN'T, I'm saying that if every manufacturer does their own thing (Tesla changes the number of CHMSL lights based on brake pressure, BMW varies intensity of the brake lights, others hit the hazards, etc, etc) it won't have the desired effect of serving as a widely-recognized indicator to other drivers.
I'd say the sudden unneccesary slowing is more of an issue that the brake lights in that case. However, you can definitely react quicker in the Model S in an emergency, since slowing starts as soon as you start lifting your foot rather than when you press the brake. Because of this, you may be able to retrain yourself to wait the extra moment to see what's happening.
Please feel free to log a safety issue against every manual transmission vehicle on the road. Speaking as a driver "receiving" you in my lane, this is a hazardous maneuver in part due to the non-warning with the immediate deceleration. I don't care how your mechanical device decelerates abruptly in my line. It could be a parachute for all I care. It's a safety hazard that should have been addressed long ago but was apparently grandfathered.
A few points.
We seem to have gotten off the OP about regen putting on perhaps just the thrid (middle) light to show that you are slowing but not applying the brake. Yes this (or amber lights or graduated lighting) would likely need NHTSA approval.
Many people posting here (Todd included) drive in a reasonable, logical and perfect fashion, They simply make the mistake of thinking others do the same (or should) and it's just not the case. These systems need to be idiot driver proof (and yes there is no such thing).
If like Knox you have the habit of putting you foot over the brake as a safety precaution (I do) then you may indeed put your brake lights on in the process which would make the next safety conscious driver behind you do the same and so on and so on. This is the reason for traffic slow ups.
Again we have had all these discussions with the Roadster 3 years ago.
This thread might brake the record for have the most break msipelllings.
We seem to have gotten off the OP about regen putting on perhaps just the thrid (middle) light to show that you are slowing but not applying the brake. Yes this (or amber lights or graduated lighting) would likely need NHTSA approval.
Many people posting here (Todd included) drive in a reasonable, logical and perfect fashion, They simply make the mistake of thinking others do the same (or should) and it's just not the case. These systems need to be idiot driver proof (and yes there is no such thing).
If like Knox you have the habit of putting you foot over the brake as a safety precaution (I do) then you may indeed put your brake lights on in the process which would make the next safety conscious driver behind you do the same and so on and so on. This is the reason for traffic slow ups.
Again we have had all these discussions with the Roadster 3 years ago.
This thread might brake the record for have the most break msipelllings.
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