another regen/brake light discussion

[ChargeIt!]

Another reason it's safer is in a panic situation. With the Roadster the brake lights come on as you're lifting the accelerator and before you make it to the brake. The car behind probably sees your brake lights a half second sooner than the same situation with an ICE car. He is alerted, and in combination with other visual cues of the emergency, will react faster.

I don't think it would be as much as 1/2 second ( because the decel has to reach the trigger point, and by then, or less-shortly-thereafter, your foot reaches the brake pedal ) -- but I nitpick -- but you make an interesting additional argument FOR ...

Out of curiosity have you ever driven a stick shift (not trying to be a jerk, just trying to find out). When driving a stick shift down shifting helps to slow down really quick, ... The other drivers are supposed to be paying attention to the cars in front of them ...

Yes, I have, and mostly in my younger days (which of course is when I drove more agressively), and mostly in Europe. Which (by coincidence) matches your other criteria: drivers seem to be more alert over there, probably due to training and more proliferation of stick-shift driving too. And, yes, you're right, agressive driving with well practiced down-shifting can result in similar decel (comparable to Roadster full throttle lift causing the reds to light up).

 

[walk_n_wind]

The regen is MUCH stronger than downshifting a standard.

Maybe in a car, but not on a motorcycle. Rapid deceleration without brake lights exits on US roads today. And I'd argue, particularly on a two wheeler, that it's on the scale of the Roadster.

I've thought probably too much about this (put most of it into this blog post), but it appears I should reserve conclusions until I drive behind a Roadster for an extended period of time...

Hey TDave, any chance you want to ride 211 one day up through Shenandoah? Maybe I'd get my chance then

 

[Doug_G]

I just had a visit from Hans (Toronto rep), and we talked about the brake light algorithm. Apparently it is sensitive to how fast you lift off, not just how much. So if it sees you suddenly lift off quickly it will turn on the brake lights. But if you just ease your speed back a bit it will not turn them on.

 

[ChargeIt!]

I just had a visit from Hans (Toronto rep), and we talked about the brake light algorithm. Apparently it is sensitive to how fast you lift off, not just how much. So if it sees you suddenly lift off quickly it will turn on the brake lights. But if you just ease your speed back a bit it will not turn them on.

Good info; thanks.

 

[AndrewBissell]

From the perspective of a European driver (where the Tesla is forbidden by law from having brake lights activated on throttle-based regen), I have to say I feel it's absence.

Quite often when driving I will dab the brake pedal once or a few times when regening in traffic just to ensure that the car behind (often close behind in heavy motorway traffic) understands I am slowing.

 

[shark2k]

Roadster regen braking is considerably stronger than any engine braking in an ICE car. Roadster regen can exceed -0.2 g's. That's a lot. I would be scared if the brake lights didn't come on with throttle lift, and I'm really glad they do.

Another reason it's safer is in a panic situation. With the Roadster the brake lights come on as you're lifting the accelerator and before you make it to the brake. The car behind probably sees your brake lights a half second sooner than the same situation with an ICE car. He is alerted, and in combination with other visual cues of the emergency, will react faster.

No doubt in my mind the brake lights need to come on with throttle lift. As someone else has mentioned, maybe the threshold could be adjusted, but only slightly.

From my understanding, engine braking in high-end sports cars (I'm talking Lambos, Ferrari's) is a lot stronger than in my puny Focus and those have no brake lights coming on. I admit I've never driven one of those (and my experience with a Roadster is very limited, 15 minute test drive at most), but from what I've heard of high-end sports cars (which the Roadster is supposed to be similar to) the regen is just like the engine braking from those cars.

-Shark2k

 

[SByer]

The 911's engine braking was about 2/3s of the Roadster's. And I definitely worried about those behind me not "getting it", especially with all the idiot drive-while-phone/texters out there.

Interesting to know that the rate of lift on the accelerator is part of the algorithm. I take back what I said, I want a little light somewhere so I can adapt my behavior!

 

[doug]

I take back what I said, I want a little light somewhere so I can adapt my behavior!

Well, they should be able to provide some sort of indicator with just a firmware update.

 

[Alpine Driver]

I am with Andrew. Its a big problem in europe that its not allowed to activate brake lights by regen only.
When I first got my car end of september 09, there was a very strong regen. I liked that, you could decrease speed say from 70km/h to 50km/h (speed inside towns) without using the brake pedal, with strong regen deceleration only.
(I would not have had a problem if there were brake lights activated ...)
In the beginning of december 09, Tesla was at my garage and installed a new firmware. Since that time, regen was much much lower. When I am in the same situation as above, I am at an speed of 62 to 65 (compared to the 50km/h with the old firmware). When I asked tesla, they told me that they had a problem with homologation and were forced to do so, as deceleration kicked in too hard and was too strong and caused too dangerous situation while not having brake lights on ...
I am not happy with that new amount of much lesser regen, but as talked to tesla, it will not be more in the near future (as rules might be changed, sometimes...)

 

[AltPowr]

I have not driven a Tesla yet, but have a reservation for a Model S in place, so I'm just going on what I read here. It just seems to me that the lights would come on based on speed. If I'm on the freeway, and I notice way ahead that I'm coming up on a car, I would let off on the accelerator pedal and coast a bit to bring my speed down. I don't want to panic someone behind me and have the brake lights come on in this case.

However, if I let off the accelerator in town, and I'm coasting up to a red light - I could see the brake lights automatically coming on at 10-15 MPH or something, because at that speed it would be obvious I'm coming to a stop.

I guess I will need to see how it really works.

 

[vfx]

.. if it sees you suddenly lift off quickly it will turn on the brake lights. But if you just ease your speed back a bit it will not turn them on.

Still hate it.

 

[vfx]

Quite often when driving I will dab the brake pedal once or a few times when regening in traffic just to ensure that the car behind (often close behind in heavy motorway traffic) understands I am slowing.

YES. User controlled. Andrew you are a genius!

 

[tomsax]

Brake Light Envy on the RAV4-EV List.

There was some discussion recently on the RAV4-EV owner list about the alarming number of vehicles that have been rear-ended and some discussion that the cause of the disproportionate number of that type of accident among the owners may be due to the lack of brake lights shown during heavy regen. There was some envy expressed over the Roadsters having the brake light on regen feature.

I would like to have some sort of indicator on the dash to let me know when the brake lights come on. I probably wouldn't want it permanently, but long enough to learn how it works so I can better understand it.

 

[ChargeIt!]

I would like to have some sort of indicator on the dash to let me know when the brake lights come on. I probably wouldn't want it permanently, but long enough to learn how it works so I can better understand it.

Yup ... see post #12 in this thread. That's 4 votes (posts #12; #13(?)=#28; #27; #33; -- did I miss someone?) for such feature. Anyone else ? Is TMI listening ? Could the firmware "flash" the "handbrake" signal while in Drive to make this indicator work (back to MY2008) ?

 

[dpeilow]

Or maybe a big red dot on the VDS.

I'd vote for it too, as it was something I was wondering about while I was backing off on the motorway during my road trip.

 

[malcolm]

Or maybe a big red dot on the VDS.

Great idea. The internal brake/regen light indicator could either be on a separate selectable/optional screen or you could set it to be something like a red frame or outline which will appear around any image which the VDS happens to be showing.

Or you could set it so that the background colour of the current VDS screen changes from blue to red, if the other two options aren't eye-catching enough.

Or you could turn it off. :biggrin:

Its a big problem in europe that its not allowed to activate brake lights by regen only.

My guess is that the regen in the EuroRoadsters has been adjusted to be closer to the equivalent engine braking?

 

[vfx]

Great idea. The internal brake/regen light indicator could either be on a separate selectable/optional screen ...

Or just make the the entire brake light coming on as a user selectable feature.

 

[vfx]

Sometimes as I come if I come up to stalled traffic jam and I'm going to the last one in line and vulnerable to a rear end collision I will step on my brake pedal a series of times to blink my lights to warn the next car coming.

With the regen light on, that is not an option.

 

[Doug_G]

Sometimes as I come if I come up to stalled traffic jam and I'm going to the last one in line and vulnerable to a rear end collision I will step on my brake pedal a series of times to blink my lights to warn the next car coming.

With the regen light on, that is not an option.

Turn on your hazard flashers. That's what the big trucks do on highways when they're moving slowly.

Doug

 

[smorgasbord]

Did we ever get a definitive answer on the algorithm for the brake lights? We've heard a accelerometer or regen, or a combination of both. As a new Roadster driver, I'm thinking that the automatic brake lights are affecting how drivers behind me are braking.

Is anyone in the SF Bay area up for some empirical testing? We'd be on a hands-free cell phones, one behind the other, noting when lights come on in various circumstances. Even if we can't reverse engineer the algorithm, we could at least potentially provide information to help drivers know when the lights are coming on.

PM me if you're interested in an experiment one weekend.