Icy Road Accident Possibly Caused By Regen

[baw]

On Friday I had my first accident with my MS. Icy conditions in Chicagoland. Was driving around 15-20mph behind a car that came to a stop at a stop sign. When I took my foot off the accelerator to slow down, I believe the regen kicked in and may have caused the vehicle to slide (instead of coast/deaccelrate smoothly). Applying the brakes did nothing at that point and I slid into the car ahead of me. Very minor accident, but damage to front bumper will require repairs.

I am not suggesting that I know with 100% certainty that this was caused by regen, but I would like to share this experience with someone at Tesla. Does anyone have any suggestions as to who a good contact would be for something like this?

Thanks in advance!

 

[Tam]

...I would like to share this experience with someone at Tesla. Does anyone have any suggestions as to who a good contact would be for something like this?...

Tesla already knows about this Regen and slippery road issue because it's being sued.

If you would like to report, just use generic Tesla Contact page. They will forward to appropriate department.

Since it is a Tesla, you now know that regen can pull your car back aggressively once you take your foot off the pedal.

You can have some options:

1) set your regen level to LOW, not standard.
2) control your pedal so your tires don't slip

I doubt those would avoid accidents when the road is slippery.

 

[bishoppeak]

Since the brakes didn't stop you in time, you were going to hit the car regardless of what regen did. Own up to this being your fault and next time apply the brakes sooner and don't follow as closely. Leave Tesla alone.

 

[Ande]

I live in northern Norway:
-brakes work just fine on ice/snow, of course, you have to have realistic speed and good tires, Tesla's still need to obey the laws of physics.
-hi regen is dangerous on ice, it feels as if regen works on rear wheels only, and certainly no not like and traction control is involved, releasing throttle on ice/ very slippery conditions, makes the ass of the car whip out and go all over the place.
It's important to note that it's a very similar feeling like driving a RWD diesel car in a low at higher speed and release the pedal. so it IS a user error. - but should be improved in software.

Sliding down an icy road (especially backwards), however, is just awful, and again, if there were some Tesla programmers that would listen, I could make them a few nice flowcharts for handling it better than best (I have extensive experience with steep, narrow, private road with turns.) Tesla should handle those conditions much better, and have lots of room for improvement.

 

[eye.surgeon]

Did you have winter tires on? Sliding into the car in front of you in November in the Midwest due to icy roads speaks directly to improper tires, regardless of regen, type of car, or driver .

 

[CameronB]

I don’t know if this is or isn’t fault of regen. And as a Californian I have precious little experience with snow and ice.

But I do recall many years ago (in a Toyota FWD car) I was driving through Utah or Colorado in bad snowy conditions. All of the traffic, including us, were crawling along at maybe 10-15mph. I remember being ultra cautious. At one point in the 20 mile super slow journey (which because of our speeds, took about 1.5 hours!), I had to his the brake to slow from my ~15mph speed to like 5mph. Talking very slow speeds here. I was being very deliberate and “light” with the brake. I don’t know if I just had some bad luck and braked while on an icy patch or what, but all of a sudden the car went into a pronounced slide - off the road. At that point, hitting the brake (and counter steering) had little to no effect...the car was sliding and presumably the tires just didn’t have any grip on the road so steering and braking didn’t do really anything. It was quite scary hitting the brake hard and trying to steer away from the shoulder of the road and having no perceived effect! Fortunately the slide was to the inside of that mountain road instead of to the outside (i.e. I didn’t go off the side of the mountain!). The car came to rest in a giant snowdrift that had been left by previous clearing attempt by a snowplow or something. Also took out one of those “snow depth rods” (yard/meter stick metal things) as our car slid through it and broke it off. Fortunately (slow speeds) no significant damage (the front license plate took a beating by hitting the measuring rod - it was all jacked up but better that than the actual car bodywork).

TL;DR: Sometimes after a car loses control on ice, further braking and steering effects are minimized or can become seemingly irrelevant.

Again, I had (and still have) limited experience with driving on icy and snowy roads. So while I was unprepared at the time from an experience point of view, I absolutely do remember being extraordinarily cautious and modulating both accellerator and brakes very smoothly and “lightly” to avoid loss of control and keeping as much distance as I could in the 10-15 mph crawl. And I still lost control.

 

[Blup85]

A always turn my ms to low regen when going up to the mountains in Northern Ca. (Winter) In my opinion regen should automatically be put to extremely low when temps drop below 36deg and the driver has to bypass that setting if they want full regen. It is of course ultimately the drivers responsibility, but not something a lot of drivers think about (My mother for instance!)

 

[CameronB]

A always turn my ms to low regen when going up to the mountains in Northern Ca. (Winter) In my opinion regen should automatically be put to extremely low when temps drop below 36deg and the driver has to bypass that setting if they want full regen. It is of course ultimately the drivers responsibility, but not something a lot of drivers think about (My mother for instance!)

This is a great idea. My BMW would warn me of potential icy conditions when the temp was 37ºF or lower. Tesla could do the same thing: “Low temperatures or potential icy conditions. Regenerative braking changed to low for added safety.”

 

[VT_EE]

A always turn my ms to low regen when going up to the mountains in Northern Ca. (Winter) In my opinion regen should automatically be put to extremely low when temps drop below 36deg and the driver has to bypass that setting if they want full regen. It is of course ultimately the drivers responsibility, but not something a lot of drivers think about (My mother for instance!)

Or have a noticeable warning below a certain temp recommending a switch to low regen. High regen is fine (and preferable) on a cold sunny day so I wouldn't want it to switch automatically.

 

[baw]

If you would like to report, just use generic Tesla Contact page. They will forward to appropriate department.

Since it is a Tesla, you now know that regen can pull your car back aggressively once you take your foot off the pedal.

You can have some options:

1) set your regen level to LOW, not standard.
2) control your pedal so your tires don't slip

I doubt those would avoid accidents when the road is slippery.

Thanks for the tips. I will certainly turn regen to LOW next time conditions are icy (just in case).

Since the brakes didn't stop you in time, you were going to hit the car regardless of what regen did. Own up to this being your fault and next time apply the brakes sooner and don't follow as closely. Leave Tesla alone.

I don't know if regen contributed to my incident or not. I said that in my original post. I do want to become more educated though and try and prevent future incidents if any settings or driving habits need to be adjusted. As a paying customer I have the right to share my experience with Tesla. It also benefits Tesla to get this feedback so they can continue to refine and improve their product (if/as needed).

Did you have winter tires on? Sliding into the car in front of you in November in the Midwest due to icy roads speaks directly to improper tires, regardless of regen, type of car, or driver .

I do not have winter tires and have never needed them with any of my previous vehicles. The roads around me are well plowed/salted and ice is actually rare.

A always turn my ms to low regen when going up to the mountains in Northern Ca. (Winter) In my opinion regen should automatically be put to extremely low when temps drop below 36deg and the driver has to bypass that setting if they want full regen. It is of course ultimately the drivers responsibility, but not something a lot of drivers think about (My mother for instance!)

Interesting idea. It seems like there are 2 schools of thought from the comments. One camp is saying that regen has nothing to do with all of this. Just need to be a better driver, have winter tires, etc.. The other camp is saying that indeed there is or could be an impact..

 

[CameronB]

This is a great idea.

This is a great idea. My BMW would warn me of potential icy conditions when the temp was 37ºF or lower. Tesla could do the same thing: “Low temperatures or potential icy conditions. Regenerative braking changed to low for added safety.”

Or how about a combination of regen to low and the new “chill” acceleration mode. In icy conditions, I imagine both would be useful in combination.

 

[pdx3181]

How does this info jibe with the theory that regen is a sort of descent control (on hills) in icy weather?

Does it still work that way to a point? And perhaps the speed here was too great?

 

[Tam]

...It seems like there are 2 schools of thought...

Low regen, no regen... all may help but I think regardless of what you do, you are pretty much out of luck when encountering slippery roads.

 

[Dax279]

It is situations like these when the "I never needed winter tires in the past" or "I've never got stuck before" quotes frustrate me the most. You never know when you will be in a situation when the additional winter tire traction would help, but the most important time is in an emergency situation. At that time why not have the best safety possible. Even if you are still in an accident, it might mean a big difference in the amount of damage or even save your life or those around you. Do yourself a favour and buy winter tires as you will be doing a favour to all of us around you by making us safer.

On the regen side, I have never had a loss of control issue with regen, but most of the time my battery is still cold for the distance that I usually travel and soni jave limited regen. With that said if I am on the highway I do tend to turn it down during the winter before starting my drive through the mountains.

 

[unbelievable]

If the regen is too strong and causes the wheels to lock up, no amount of braking is going to cause them to unlock. Locking the wheels in this situation is the worst situation to be in, as proper control of the vehicle is impossible. If regen had not been on, the OP might have had the opportunity to come off the accelerator and gently steer and brake in order to avoid hitting the stopped car, all without the wheels locking.

I think this is an absolutely valid reason to contact Tesla. An ideal situation in this circumstance would be for the regen to release until it feels traction, thereby returning control to the driver. Or behave like ABS in order to give the driver the ability to attempt to steer around a possible accident.

 

[Tam]

...If the regen is too strong...

You can ease the pedal off just enough to let the car coast. You can monitor your progress with the energy consumption graph on the instrument cluster--orange means you are accelerating, green means you are doing a regen, if you are not orange nor green then you are at the point of coasting.

Or you can shift the car to neutral if you don't want any regen effect.

 

[unbelievable]

You can ease the pedal off just enough to let the car coast. You can monitor your progress with the energy consumption graph on the instrument cluster--orange means you are accelerating, green means you are doing a regen, if you are not orange nor green then you are at the point of coasting.

Or you can shift the car to neutral if you don't want any regen effect.

Whilst that is absolutely true, in the event of having to make an emergency stop, monitoring the colour of the energy consumption graph in order to bring the car to a safe stop is possibly not ideal.

 

[thegruf]

sorry to hear of the OP's minor bump

this biggest point is - don't forget Model S is 2+ tons.
Physics dictates 2+ tonnes requires more force than a typical ICE <1.5ton car to stop in a given distance
For the same stopping distance this requires more traction from the tires.
With ice + snow only a restricted amount of traction is avaiable.

Leave greater distance for braking because it is a heavy car.
Be less abitious with speed on curves in icy conditions.
Be more inclined to put winter tires on than you would for a smaller lighter car if there is a chance you could encounter even occasional wintry conditions. And yes, regen on low is to be recommended.
Drive safely ... because if nothing else repairing your Tesla is expensive and frequently time consuming.

 

[Blup85]

Do we know if the regen reduces while decelerating when wheel slipping occurs like when you accelerate?
I'm not familiar with driving a dual motor vehicle, but using regen to decelerate in icy conditions is not so easy with a rwd on high regen, because now I'm only using two rear wheels to slow down (also weight transfer foward would reduce breaking potential as well?)and expecting someone to feather the accelerator ( notice i didnt say gas pedal) pedal while feathering the brakes is just silly, or putting the car in nuetral..
Again, I'm not taking the responsibility from the driver, but it adds complexity that doesn't need to be there.
I'll be testing this out for sure the next opportunity I get (safely of course)

 

[Dax279]

Do we know if the regen reduces while decelerating when wheel slipping occurs like when you accelerate?
I'm not familiar with driving a dual motor vehicle, but using regen to decelerate in icy conditions is not so easy with a rwd on high regen, because now I'm only using two rear wheels to slow down (also weight transfer foward would reduce breaking potential as well?)and expecting someone to feather the accelerator ( notice i didnt say gas pedal) pedal while feathering the brakes is just silly, or putting the car in nuetral..
Again, I'm not taking the responsibility from the driver, but it adds complexity that doesn't need to be there.
I'll be testing this out for sure the next opportunity I get (safely of course)

I unfortunaltey have not noticed, but I actually felt that regen made me slow and stop in a more controlled fashion than just using the breaks last year in the winter.