Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

ibooster braking system logic issue [and discussion around brake failure claim in shanghai]

skywalker2go

Member
Apr 26, 2021
13
-8
China
Double check your basic logic. Telsa has a million cars on the road and 1 (crazy) woman says she thinks that maybe her dad thinks that maybe he hit the brakes as he sped thru town.

Do the math and you'll see that Tesla brakes are *exactly* 100% reliable. That's why everyone is sure it's the driver's fault.

Could Zhang's car have a 1-in-a-million brake failure? Maybe but it's extremely unlikely. Could it have a brake failure that somehow fixed itself without leaving any evidence? No. That has never happened on any car from any maker anywhere ever.
At least 4 points to add.

1、Ms. Zhang's case is not the only one.
She is in fact the one who starts a war against Tesla in public. Almost every fews days there will be one Tesla accident declaring to encounter brake malfunction and SUA. Check regularly the
Chinese Tweet-like platform Weibo will easily prove.
2、Once reported, any possible design defect should be investigated completely, no matter whether it exists or not and how small the possibility is.
3、Even if other brands may suffer more accidents, if they are clearly proved to be drivers' faluts, then the brand is not responsible. However, for Tesla, it's not the case. Obviously, the public are not fully convinced that all these accidents are drivers' faults.
4、One step back, even if Tesla's braking system gets eventually proved to be bug-free, Tesla may also needs to reflect after so many cases, whether its operation logic needs further improvement.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,836
9,800
Riverside Co. CA
At least 4 points to add.

1、Ms. Zhang's case is not the only one.
She is in fact the one who starts a war against Tesla in public. Almost every fews days there will be one Tesla accident declaring to encounter brake malfunction and SUA. Check regularly the
Chinese Tweet-like platform Weibo will easily prove.
2、Once reported, any possible design defect should be investigated completely, no matter whether it exists or not and how small the possibility is.
3、Even if other brands may suffer more accidents, if they are clearly proved to be drivers' faluts, then the brand is not responsible. However, for Tesla, it's not the case. Obviously, the public are not fully convinced that all these accidents are drivers' faults.
4、One step back, even if Tesla's braking system gets eventually proved to be bug-free, Tesla may also needs to reflect after so many cases, whether its operation logic needs further improvement.

(personal opinion post only, not related to moderation, or representing TMC or anyone else but myself)

This is why I said "skeptical" when you started off posting with the long video. You have a 100% right to your opinion, but from here, it also seems pretty obvious you have an axe to grind or a particular message you want to try to push. There isnt "so many cases". There isnt a single documented, proven failure, but thats the narrative you are trying to push. "Tweets on weibo" (or twitter, or any other social media platform) is not "proof" of anything.

Anyone can report anything, so no, all reports are not credible. If someone reports something but then refuses to let someone else look at it, they instantly (to me anyway) lose ALL credibility.

I can say something like "look at me, I can turn this iron into gold!", and refuse to let anyone see my method or examine the before and after pieces. Should I be taken credibly at that point? (its a rhetorical question, the answer is "no")

In any case, No, tesla does not have to "prove their braking system is bug free" as you keep saying. People reporting failures need to prove that it wasnt them. If you dont trust teslas brakes, then simply buy another car. Everyone has to make their own choices, and is entitled to their own opinions, but from here, that doesnt look like what you are after.
 

sroy

Closed
Mar 13, 2021
542
224
New Jersey
You don't investigates claims that makes zero sense. You investigate claims that are credible. Brake failure on Tesla is not a credible claim. Telsa has the best safety record in the industry and now has MILLIONS of cars on the roads.

To date there is an estimated 22.5 BILLIONS miles driven by Tesla collectively. There is no brake failure.

To go back on topic: OP asked about this one brake failure case wondering about potential brake issue(s) on Tesla vehicles. The collective wisdom on this board is that there are no brake issues. The investigation on the reported case as well as comparison with brake tests strongly indicates that, once again, Tesla is not at fault.

If you still believe Telsa brakes are problematic, do yourself a favor and don't buy a Tesla.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
10,202
5,108
I think what you described here should be called 2 assumptions in stead of 2 facts. But what i list below could be proved either by public paperwork or recorded videos and images.

1、Before the accident happened, Miss Zhang's family ( her parents, Ms. Zhang, and her 1-year-old niece ) were in the car. The accident happened at about 6 pm on the urban road. Her father was a truck driver with more than 30 years experience.
You left out a critical detail:
The police report said the cause of the accident was insufficient following distance. This was reported back in March by other media, so this is not Tesla's claim, and likely is true:
Tesla Responds to Braking System Failure Controversy in China Amid Social Media Frenzy - Pandaily

Tesla on 4/28 posted the following account that actually Tesla customer service called her immediately after getting an accident alert, and where she said the following (bold emphasis mine):
"On February 21, 2021, Mr. Zhang, the father of Ms. Zhang, the “rights defender” at the Shanghai Auto Show, carried four of his family members and collided with other vehicles while driving along National Highway 341. Later, Tesla 400 customer service called Ms. Zhang. During the communication, Ms. Zhang reported that she was playing with a mobile phone in the passenger seat at the time. It was her father who was driving, and she felt that the speed of the car caused a crash. On the evening of the same day, the traffic police judged that Mr. Zhang was fully responsible for the accident because he did not maintain a safe distance from the vehicle in front."
Link to article below (unfortunately Google translate link doesn't work, it keeps redirecting, those in USA like me would need to use your browser's Google Translate plug-in to translate or copy/paste the text into google translate):
头条文章
You may say this is all Tesla's own account, but at the very least we know the police report is likely fact, as it was reported by other media way back in March (and this can be verified by asking the police department). The customer service hotline may also have a recording of Ms. Zhang's conversation, although legally they may not be able to release it to the public.
2、Ms. Zhang refused to accept Tesla's assigned third party for inspection. And Tesla did not admit any other third party's result.
My understanding is Ms. Zhang has refused ANY inspection of her car. Not just Tesla's, but she is not agreeing to any inspection of her car, nor has she done an inspection herself! That is what raised red flags for me in the first place. If she wanted the truth, she should demand an inspection, if not by Tesla, a third party, or her own party, at least by the government (which can force a recall, just like they did for the suspension back in October last year).
I don't believe Tesla has said Ms. Zhang must use their designated third party, Tesla has publicly said they are willing to accept any third party's examination, including the government doing a full investigation into their braking system.
One of these certificates provided by Tesla‘s assigned partner marked M3 as front wheel drive.
3、Ms. Zhang has tried to negotiate with Tesla for many times. Tesla promised to help resell the car to someone else. Ms. Zhang considered that to be immoral and refused.
From the initial reports Tesla offered to repair the vehicle. That is what normally people do. Even if there really was a brake defect, after investigating the cause, the vehicle's brakes can be repaired and safely put back on the road. That is how lemon laws work in the USA also, the manufacturer is given a chance to repair the vehicle; if they can't, then the vehicle may be disposed of. Also when a recall happens, the manufacturer repairs the vehicle, they don't trash the old ones and give new ones to customers! Of course none of this can happen without inspecting the vehicle and finding if there is really a problem and what is the cause!
4、After the protest, Tesla's VP declared in public "Never compromise", and "Some one must be behind Ms. Zhang", without providing any proof. Apologizes are issued later after the government made some comments.
5、Ms. Zhang has always demanded EDR info, especially brake pedal distance related data. Tesla did provide some data, but did not include the most critical pedal distance related info. No further response made.
You left out that Ms. Zhang has long claimed that Tesla falsified their records, claiming that the 118.5 km/h speed is made up (claiming that her father was not speeding at the time, the road had a 80km/h limit). Tesla is wasting their time if all Ms. Zhang does is claim that Tesla changed their records after Tesla provided them. It's pretty clear Ms. Zhang will not accept any fact that goes against her argument.

Also the latest news is on 4/2 Tesla has provided all information they have on the car already from 30 minutes before the accident (from the same weibo post linked before):
"On April 22, the staff of Tesla's special working group contacted Ms. Zhang's husband, Mr. Li, by phone and text messages many times, but there was no answer or reply. On the same day, Tesla’s customer support department sent the electronic stamped version of the vehicle data 30 minutes before the accident via company email to the personal mailbox registered by Ms. Zhang when buying the car, and sent the sealed paper stamped version of the vehicle data by express. Send it to the contact address registered when Ms. Zhang bought the car."

Another choice bit from that article, that calls into question the credibility of Ms. Zhang:
"On April 19, Ms. Zhang conducted a radical “rights defense” at the Tesla booth at the Shanghai Auto Show. Claiming to be three months pregnant (it was later confirmed by the police that she was not pregnant)."

As for the EDR, that requires access to the vehicle to download from the "black box" with a special tool. If Ms. Zhang refuses any party to touch the vehicle, how is Tesla going to provide that?

In North America, actually you can download the EDR yourself with a tool you can buy from an authorized third party.
Event Data Recorder
Tesla no longer offers this tool nor the data translation service outside North America, however, because some people tried using the tool to hack/reverse engineer Tesla's system (even though this was never attempted on similar Bosch tools for Hyundai/Kia and Subaru):
"there have been some who have made an effort to reverse engineer the Tesla system - whether on the hardware or software side. While such behavior was never observed to such a degree with respect to the Bosch CDR Tool and doesn't seem to have been undertaken for other tools such as, for example, the Hyundai or Kia Tool or the Subaru Tool, for whatever reason, the Tesla tool seems to have been the first such attack on system integrity. My perspective on this might be summed this way: "play stupid games, win stupid prizes."
Tesla EDR- no data flow from RCM - CrashForum.info
Tesla hesitancy may be related to this (data may be sold to other third parties to reverse engineer Tesla's system, with Tesla knowing there have already previous attempts by actors outside North America).
As a comparison, another brand also encountered similar accidents, then they released full logs and detailed EDR info. Shortly after that the public stopped criticizing that brand.
Link to that incident? Was that done with that brand not even getting a chance to examine the vehicle? The fact is Ms. Zhang is requesting a full refund of the vehicle plus damages all on her word that the brakes were defective and with no examination of the vehicle. She had also already claimed that Tesla has falsified the data provide so far to her (including disputing the 118.5 km/h speed which is highly unfavorable to her case).
Above are just parts of the facts available, I did not mention them before because i think they would make people emotional and also contribute little to the final analysis.
IMO, for a video that tends to tell the whole story, i think at least a few points above should be mentioned, otherwise people may think that Tesla belongs to the vulnerable groups, which is obviously not true, at least in China.
Sure, we can discuss the facts, but let's not leave out important details. While we can't say 100% that zero Model 3 in China have brake problems, from the facts so far for Ms. Zhang's particular case the only evidence presented of a brake defect is her word that the brakes are defective. There is zero other evidence and she has refused any examination of the vehicle. All the facts shown so far suggest this is a simply case of a typical rear end accident where the driver was going a bit too fast and not leaving enough stopping distance.

There really is not much Tesla can do at this point. Even assuming the brakes were defective, an examination of the vehicle is required to find the problem, as there are many possible causes of brake failure. China's government also appears to refuse to step in. If there really was serious braking system complaints with Teslas, here in the USA the NHTSA/NTSB would have long stepped in to investigate. As I linked before NHTSA already investigated SUA claims in the USA and found they were all caused by driver error, no evidence of defect with Tesla's system.
 
Last edited:

sunjack

Member
Apr 20, 2021
28
2
Shanghai, China
There really is not much Tesla can do at this point. Even assuming the brakes were defective, an examination of the vehicle is required to find the problem, as there are many possible causes of brake failure. China's government also appears to refuse to step in. If there really was serious braking system complaints with Teslas, here in the USA the NHTSA/NTSB would have long stepped in to investigate. As I linked before NHTSA already investigated SUA claims in the USA and found they were all caused by driver error, no evidence of defect with Tesla's system.
The government is investigating, just haven’t release any results yet (I am waiting). As for Ms. Zhang’s case, they can’t force her to turn over her car. The government can only facilitate the negotiations between both parties. And Ms. Zhang has been arrested (and released now) for what she did.
 

skywalker2go

Member
Apr 26, 2021
13
-8
China
You left out a critical detail:
The police report said the cause of the accident was insufficient following distance. This was reported back in March by other media, so this is not Tesla's claim, and likely is true:
Tesla Responds to Braking System Failure Controversy in China Amid Social Media Frenzy - Pandaily

Tesla on 4/28 posted the following account that actually Tesla customer service called her immediately after getting an accident alert, and where she said the following (bold emphasis mine):
"On February 21, 2021, Mr. Zhang, the father of Ms. Zhang, the “rights defender” at the Shanghai Auto Show, carried four of his family members and collided with other vehicles while driving along National Highway 341. Later, Tesla 400 customer service called Ms. Zhang. During the communication, Ms. Zhang reported that she was playing with a mobile phone in the passenger seat at the time. It was her father who was driving, and she felt that the speed of the car caused a crash. On the evening of the same day, the traffic police judged that Mr. Zhang was fully responsible for the accident because he did not maintain a safe distance from the vehicle in front."
Link to article below (unfortunately Google translate link doesn't work, it keeps redirecting, those in USA like me would need to use your browser's Google Translate plug-in to translate or copy/paste the text into google translate):
头条文章
You may say this is all Tesla's own account, but at the very least we know the police report is likely fact, as it was reported by other media way back in March (and this can be verified by asking the police department). The customer service hotline may also have a recording of Ms. Zhang's conversation, although legally they may not be able to release it to the public.

My understanding is Ms. Zhang has refused ANY inspection of her car. Not just Tesla's, but she is not agreeing to any inspection of her car, nor has she done an inspection herself! That is what raised red flags for me in the first place. If she wanted the truth, she should demand an inspection, if not by Tesla, a third party, or her own party, at least by the government (which can force a recall, just like they did for the suspension back in October last year).
I don't believe Tesla has said Ms. Zhang must use their designated third party, Tesla has publicly said they are willing to accept any third party's examination, including the government doing a full investigation into their braking system.

From the initial reports Tesla offered to repair the vehicle. That is what normally people do. Even if there really was a brake defect, after investigating the cause, the vehicle's brakes can be repaired and safely put back on the road. That is how lemon laws work in the USA also, the manufacturer is given a chance to repair the vehicle; if they can't, then the vehicle may be disposed of. Also when a recall happens, the manufacturer repairs the vehicle, they don't trash the old ones and give new ones to customers! Of course none of this can happen without inspecting the vehicle and finding if there is really a problem and what is the cause!

You left out that Ms. Zhang has long claimed that Tesla falsified their records, claiming that the 118.5 km/h speed is made up (claiming that her father was not speeding at the time, the road had a 80km/h limit). Tesla is wasting their time if all Ms. Zhang does is claim that Tesla changed their records after Tesla provided them. It's pretty clear Ms. Zhang will not accept any fact that goes against her argument.

Also the latest news is on 4/2 Tesla has provided all information they have on the car already from 30 minutes before the accident (from the same weibo post linked before):
"On April 22, the staff of Tesla's special working group contacted Ms. Zhang's husband, Mr. Li, by phone and text messages many times, but there was no answer or reply. On the same day, Tesla’s customer support department sent the electronic stamped version of the vehicle data 30 minutes before the accident via company email to the personal mailbox registered by Ms. Zhang when buying the car, and sent the sealed paper stamped version of the vehicle data by express. Send it to the contact address registered when Ms. Zhang bought the car."

Another choice bit from that article, that calls into question the credibility of Ms. Zhang:
"On April 19, Ms. Zhang conducted a radical “rights defense” at the Tesla booth at the Shanghai Auto Show. Claiming to be three months pregnant (it was later confirmed by the police that she was not pregnant)."

As for the EDR, that requires access to the vehicle to download from the "black box" with a special tool. If Ms. Zhang refuses any party to touch the vehicle, how is Tesla going to provide that?

In North America, actually you can download the EDR yourself with a tool you can buy from an authorized third party.
Event Data Recorder
Tesla no longer offers this tool nor the data translation service outside North America, however, because some people tried using the tool to hack/reverse engineer Tesla's system (even though this was never attempted on similar Bosch tools for Hyundai/Kia and Subaru):
"there have been some who have made an effort to reverse engineer the Tesla system - whether on the hardware or software side. While such behavior was never observed to such a degree with respect to the Bosch CDR Tool and doesn't seem to have been undertaken for other tools such as, for example, the Hyundai or Kia Tool or the Subaru Tool, for whatever reason, the Tesla tool seems to have been the first such attack on system integrity. My perspective on this might be summed this way: "play stupid games, win stupid prizes."
Tesla EDR- no data flow from RCM - CrashForum.info
Tesla hesitancy may be related to this (data may be sold to other third parties to reverse engineer Tesla's system, with Tesla knowing there have already previous attempts by actors outside North America).

Link to that incident? Was that done with that brand not even getting a chance to examine the vehicle? The fact is Ms. Zhang is requesting a full refund of the vehicle plus damages all on her word that the brakes were defective and with no examination of the vehicle. She had also already claimed that Tesla has falsified the data provide so far to her (including disputing the 118.5 km/h speed which is highly unfavorable to her case).

Sure, we can discuss the facts, but let's not leave out important details. While we can't say 100% that zero Model 3 in China have brake problems, from the facts so far for Ms. Zhang's particular case the only evidence presented of a brake defect is her word that the brakes are defective. There is zero other evidence and she has refused any examination of the vehicle. All the facts shown so far suggest this is a simply case of a typical rear end accident where the driver was going a bit too fast and not leaving enough stopping distance.

There really is not much Tesla can do at this point. Even assuming the brakes were defective, an examination of the vehicle is required to find the problem, as there are many possible causes of brake failure. China's government also appears to refuse to step in. If there really was serious braking system complaints with Teslas, here in the USA the NHTSA/NTSB would have long stepped in to investigate. As I linked before NHTSA already investigated SUA claims in the USA and found they were all caused by driver error, no evidence of defect with Tesla's system.

Since this facts-listing game is meaningless and endless (Tesla and Ms. Zhang are still in the loop), I will not continue. The reason why I mention and my attitude towards them have already been clearly stated in last comment.
Considering this discussion now is far off topic, evolving gradually into war of words. I would like to share some of my personal thoughts and try to end disscusion in this direction.

1) I‘m afraid both sides are hiding some truth, which may matter a lot.
According to previous analysis, ABS was likely to be activated in these accidents (stiff pedal). Whether they were properly activated may be the most critical factor. In this sense, speed and pedal distance related info would be the most valuable data.
Tesla has released speed info, pedal distance not included. I think all these data stay already in Tesla's database and there is no need to download EDR inside the car. That's a suspicious point. Will Tesla make this info public if required and allowed ( to go inside the car )?
As for Ms. Zhang, whether his father was actually driving too fast remains the largest doubt. That road happens to have no cameras installed and she is unable to provide any solid proof. That's indeed very suspicious. Is it possible that the driver pressed accelerator by mistake?

2) The real challenging part of this accident is how the truth could be investigated by third party organizations or national authority. Most people speculate that could be a bug in software instead of hardware defect. If this is the case, then it's indeed very difficult to verify and almost impossible for individuals like Ms. Zhang. Consider toyota brake failure event as a reference.

At current stage I personally still hope Tesla can help conduct further investigations and sweep all the doubts, which may strengthen the confidence in consumers but seem impossible according to what you guys mentioned above.
 

Electric Dream

Pilots the Millennium Milkfloat
Jul 21, 2016
1,682
2,759
UK
You keep talking about "pedal distance". There is no sensor I'm aware of that measures pedal travel (if that's what you mean),
The data available from a model 3 is brake pressure measured at the master cylinder and that data has been released.
You also say it's doubtful Mr Zhang was driving too fast. Teslas has already confirmed that "the speed of the vehicle before depressing the brake pedal was 118.km/h".

Ms Zhang has refused to cooperate and is obviously trying to get a pay out, but she's not going to be successful. No further investigation is necessary and you may as well give up your crusade because it's not going to get you anywhere either.
 
  • Like
Reactions: Big Earl

charlieaf92

Member
Nov 9, 2020
66
35
cincinnati
This is stupid. Someone gets in an accident in wet/slippery conditions and blames the brakes. Occam's Razor does a pretty good job of handling situations like this. Even without assistance there should be a direct connection between the pedal and the brake system, just like any other car. If a normal ICE car stalls out while you're driving, you lose all boost assistance as well - just press harder.

Who to believe?

1) A few random people on Youtube
or
2) The engineers at Tesla who literally designed and wrote the software, have every diagnostic tool in the world available, plenty of vehicles, a test track, etc, etc

I'd bet the folks at Tesla would recreate an identify it first, and even if the random Youtubers miraculously figured it out at the same time, there would already have been a software update pushed and the problem would be ancient history.

I've driven my model 3 on snow and ice. Purposely gone into several inches of snow in a parking lot to try out drift mode. The brakes work exactly like they should - however I did find that when the roads are slippery it takes longer to stop than on dry roads.

(moderator note: edited post slightly to remove disparaging remarks. Please be mindful of remarks denigrating an entire region)
 
Last edited by a moderator:

TunaBug

Member
Mar 27, 2021
35
26
Kirkland, WA
I can tell you now what the cause of this and other 'pedal misapplications' is. It's actually quite simple:
  • Drivers of EVs with regen are becoming less and less familiar with the brake pedal, how it feels and how to use it properly when required.
  • Drivers do maybe one emergency stop during their driving test and then rely on the car they drive thereafter to do the emergency braking for them with AEB etc.
  • Drivers are becoming less and less familiar with how a car works generally, how to operate it and what to do when things go wrong.
There's no way back from this because cars are only going to become more autonomous, so driving skills will wane and only enthusiasts will want to learn how to drive a car manually and with a degree of skill.

Some will say it's progress, some will say it's inevitable.
The result is the car is going to blamed for anything and everything bad that happens.
The owner will accept no responsibility.
This is the start of that.

Those reasons are similar to what I was speculating about above. I'll add another: in an ICE you get lower power when starting out from zero, so if you press the accelerator instead of the brake then you have more time to react or do less damage if you fail to react. With an EV you have full power from zero RPM so there's less time and/or more damage.

Note that there are significant items in a car that a required by by current laws that were put there not because of defects in the cars, but to reduce damage when somebody screws up. When I was a kid not all cars came with seatbelts and headrests were uncommon. It wasn't the car manufacturers' fault if I got permanently injured when somebody rear-ends me while in a 1960's bench seat with no headrest: it was the norm to not have them, they weren't required, and many drivers would be happy to save a few bucks by not paying for them. No different for seatbelts.

Nothing in this thread makes me think there is a problem with Tesla's brakes. But I do worry that if enough people injure themselves by accidentally hitting the accelerator that we might see additional regulations around that.
 

Tam

Well-Known Member
Nov 25, 2012
8,778
7,602
Visalia, CA
Since the brake failure protest at Shanghai Auto Show, Tesla has publicly released the 30-minute log.

What puzzles me is the driver was applying brakes more than 40 times during that time for a high speed driving above 100km/hr (62mph).

Could it be that the driver was driving with 2 feet instead of one? Could it be that the driver was using the braking pedal as a way of slowing down instead of letting go of the accelerator pedal?

Could it be that this driver didn't have training on how to drive with one foot?


(moderator note: moved this post which was a separate thread, into this thread since the meat of this discussion is in this thread)
 
Last edited by a moderator:

Tam

Well-Known Member
Nov 25, 2012
8,778
7,602
Visalia, CA
...Is it possible that the driver pressed accelerator by mistake?...

It's more like driving with 2 feet and not 1 foot.

The press reports that the 30-minute log shows the driver drove at a high speed above 100 km (62MPH) and applied the brakes more than 40 times.

I've seen that before. They like to press on the accelerator and instead of easing it off, they would prefer to get another foot and lightly press on the brake pedal to control the speed.

2-foot driving is unnecessary because Model 3 has so much regen braking power that by easy off your accelerator, it's just like applying the real brake with the other foot.

I think 2-foot driving is a bad habit to control speed and may result in accidents such as this.

...pedal distance not included.
No "pedal distance" but yes for the force of pressing on the brake pedal.

When the car accelerated to 118 km/hr (74MPH, the force on the pedal was too light 0.3 bar out of 140.7 bar.

But because of that light press on the brake, the speed went down to 116 km/hr (72MPH).

The additional force from 4.5 to 12.3 bar (still too light out of 140.7 bar) resulted in the speed reduction to 94 km/hr (58MPH).

When the driver was not pressing on with enough force at the last seconds, the AEB (Automatic Emergency Brake) was helping to get the force of applying the braking pedal to all the way 140.7 bar and resulted in the slow speed of 48.5 km/hr (30MPH).



I think all these data stay already in Tesla's database and there is no need to download EDR inside the car.
It's needed to verify to see whether there is any discrepancy between the log in the memory card and the over-the-air transmission logs.

...Will Tesla make this info public if required and allowed ( to go inside the car )?...

Just go to court and the court can order Tesla what to do. The court can assign China Transportation Bureau to verify what they find in the car.

It's just like the 2016 Gao Yaning's Tesla car fatal accident. The court allowed a third party (not Tesla staff) to access the car wreckage to retrieve the car's log to see whether the Autopilot was on or off.

The car wreckage is with the Gao's family. With the help of third-party experts, they can disclose the info any way they want without the need for Tesla staff.

...Most people speculate that could be a bug in software instead of hardware defect...
The bug here is which school taught him how to drive with 2 feet in a Tesla? One on the accelerator pedal and one on the brake pedal.

That bug is not safe at all. The teaching needs to be reprogrammed.

...At current stage I personally still hope Tesla can help conduct further investigations and sweep all the doubts...

I think Tesla's release of the car log is pretty much straightforward.

Further investigations will be who taught the driver to brake more than 40 times in just 30 minutes with a high speed of over 100 km/hour (62MPH). Should the license of that school be revoked?
 

Big Earl

bnkwupt
Jul 12, 2017
5,296
9,758
Springfield, VA
It’s impossible to two-foot a Model 3. Pressing the brake *at all* immediately kills all of the power. If, while riding the brake, you release and reapply the accelerator pedal, you will only get a very modest amount of power... perhaps 20 horsepower with the pedal to the floor.

I tried it out a couple of years ago when a driver’s education teacher was inquiring about using the Model 3 as an instruction vehicle. I tried it out again last month when testing out a pedal misapplication scenario that happened to someone in our local EV group. Same behavior in all of the tests, as expected.

In my opinion, the driver was tailgating and driving manner that required frequent, strong braking; more aggressive than what regen provides.

He ultimately bit off more than he could chew and ran into the back of someone, despite the car applying emergency braking. The car applying emergency braking mitigated the damage from the accident and likely prevented injury. It also demonstrates that the brakes worked fine.
 
Last edited:

stopcrazypp

Well-Known Member
Dec 8, 2007
10,202
5,108
Since this facts-listing game is meaningless and endless (Tesla and Ms. Zhang are still in the loop), I will not continue. The reason why I mention and my attitude towards them have already been clearly stated in last comment.
Considering this discussion now is far off topic, evolving gradually into war of words. I would like to share some of my personal thoughts and try to end disscusion in this direction.

1) I‘m afraid both sides are hiding some truth, which may matter a lot.
According to previous analysis, ABS was likely to be activated in these accidents (stiff pedal). Whether they were properly activated may be the most critical factor. In this sense, speed and pedal distance related info would be the most valuable data.
Knowing the pedal distance will tell you nothing extra because the data will look exactly the same in both situations, whether it was a stiff pedal or whether the driver didn't press it enough (which appears to be the case given the AEB, Automatic Emergency Braking activated to help apply more braking pressure).

A lot of people seem to think that Tesla's brake pedal is "electronically" connected like the accelerator pedal is, meaning:
pedal > sensor > computer > brake booster pump > master cylinder > brakes

You seem to be thinking the same, that somehow the brake pedal is a "controller" that is not mechanically connected to the booster pump and master cylinder. This is not how it works.

Instead it is mechanically connected exactly like conventional braking systems:
pedal > brake booster pump > master cylinder > brakes

See diagram from Bosch on how the iBooster (Model 3 uses gen 2) is connected (the blue lines are the actual brake fluid lines):
iBooster.jpg

I suggest looking at the video from Bosch's iBooster website for more details.
iBooster

People with Teslas can tell you on Autopilot (or when "Hold" mode is used where it applies mechanical brakes) the brake pedal will actually move by itself depending on how much mechanical brakes are applied. This is not true of the accelerator pedal (it does not move).

While the booster pump can be electronically actuated by the car system, it is always mechanically connected to the brake pedal, so the driver can always mechanically apply more braking with the pedal than whatever the car computer is doing. That is why in a video I previously linked, the journalist said it's almost impossible for the brake system to completely fail, as the mechanical brakes will always work (even if all power is lost to the car and booster pump).
Tesla has released speed info, pedal distance not included. I think all these data stay already in Tesla's database and there is no need to download EDR inside the car.
There is some data sent to Tesla automatically when an accident happens. However, I doubt it will be as detailed as the EDR, as it must be sent using 4G internet, so the files can't be too big. When accidents happen, the investigators always download the data from the EDR, they don't rely on the data Tesla got remotely.
That's a suspicious point. Will Tesla make this info public if required and allowed ( to go inside the car )?
Even Tesla's EDR does not appear to record brake pedal position other than "on" or "off" (reasons likely as I explained above).
This is what it records for the brakes in the EDR:
"Service Brake indicates the status of the driver’s application of the brake pedal as reported by the brake booster. The possible values for Service Brake are “On” (pedal being applied by driver) and “Off” (pedal not being applied by driver)."
The Accelerator pedal position is what is recorded:
"Accelerator Pedal (%) is the percent of full application of the accelerator pedal. The resolution of Accelerator Pedal (%) is to the nearest percent."
https://www.crashdatagroup.com/pdf/Tesla-sample-EDR-Report-Y.pdf

There is a pedal travel sensor inside the iBooster Module itself and appears to be used to provide data for blending regen braking and for the iBooster itself to control brake boost. However, Tesla does not appear to use this signal given they do not blend regen braking using the brake pedal (Tesla uses the accelerator pedal). They only use the brake pedal "on/off" signal to actuate the brake lights and also as an input to disable automation functions (and things like starting the car).

As I mention above however, given the pedal is mechanically connected (not an independent electronic controller), knowing the pedal travel does not tell you how much effort the driver has applied to the brakes, especially if the theory of "failure" is that the pedal gets "harder".
iBooster_Diagram.jpg


As for Ms. Zhang, whether his father was actually driving too fast remains the largest doubt. That road happens to have no cameras installed and she is unable to provide any solid proof. That's indeed very suspicious. Is it possible that the driver pressed accelerator by mistake?
From Tesla's logs, the driver did not press the accelerator by mistake. The driver first applied only a little bit of braking, then applied more braking. Tesla's AEB activated to brake further, however it was not enough to stop the car fully before he crashed. It is not like other SUA cases where no brakes were applied.
2) The real challenging part of this accident is how the truth could be investigated by third party organizations or national authority. Most people speculate that could be a bug in software instead of hardware defect. If this is the case, then it's indeed very difficult to verify and almost impossible for individuals like Ms. Zhang. Consider toyota brake failure event as a reference.

At current stage I personally still hope Tesla can help conduct further investigations and sweep all the doubts, which may strengthen the confidence in consumers but seem impossible according to what you guys mentioned above.
The issue is the guess that it is a "software bug" is all blind speculation (as I point out, likely mostly from people thinking Tesla's brake pedal is a "controller" for the computer, not mechanically connected). There are many possible hardware and mechanical causes of brake failure (which I pointed out before, like leak/air/water in lines/reservoir, broken booster pump, broken or dirty electrical connections, etc) that have not been investigated yet given Ms. Zhang refuses, and a honest investigation would look for those also. Those assuming a "software" issue straight out are coming in with a biased mind already, not with an objective mind to look at all possible causes, even assuming Ms. Zhang's car really had a brake problem.
 
Last edited:

Electric Dream

Pilots the Millennium Milkfloat
Jul 21, 2016
1,682
2,759
UK
By the way, has anyone seen any reliable information about the road/weather conditions at the time of the collision? I don't recall reading anything about that but I might have missed it in all the noise.
 

Tam

Well-Known Member
Nov 25, 2012
8,778
7,602
Visalia, CA
It’s impossible to two-foot a Model 3. Pressing the brake *at all* immediately kills all of the power. If, while riding the brake, you release and reapply the accelerator pedal, you will only get a very modest amount of power... perhaps 20 horsepower with the pedal to the floor...

I just tried it out on my 2018 Tesla Model 3 Long Range and although there are audio and visual alarms, they don't interfere with driving with two feet and with two pedals depressed at the same time.

I would not recommend it but for those who are addicted to two pedals depressed at the same time, I can see how they like it in Model 3. They can regulate the speed with the brake pedal and not just the accelerator pedal all at the same time. It becomes an art which again, I do not endorse.

It's possible to fine-tune the art so instead of lifting the accelerator pedal frequently, they can adjust the brake pedal pressure 40 times per 30 minutes.

I would say that takes practice, especially I have to ignore the alarms. But they are not really loud so it's not that distracting at all.

 
  • Informative
Reactions: Traguar

stopcrazypp

Well-Known Member
Dec 8, 2007
10,202
5,108
I just tried it out on my 2018 Tesla Model 3 Long Range and although there are audio and visual alarms, they don't interfere with driving with two feet and with two pedals depressed at the same time.

I would not recommend it but for those who are addicted to two pedals depressed at the same time, I can see how they like it in Model 3. They can regulate the speed with the brake pedal and not just the accelerator pedal all at the same time. It becomes an art which again, I do not endorse.

It's possible to fine-tune the art so instead of lifting the accelerator pedal frequently, they can adjust the brake pedal pressure 40 times per 30 minutes.

I would say that takes practice, especially I have to ignore the alarms. But they are not really loud so it's not that distracting at all.

You can see from the video almost no brake pressure is being applied though, and even so the speed has reduced in the video (so the power from the motor must be quite low). The two pedal mode is there because this is almost a necessity in hilly areas for a lot of drivers. The brake "hold" mode does help, but it's still more jerky and less confidence inspiring than 2 pedal.

I think the point however of the comment you were responding to is that the power is so low in 2 pedal it's trivial to overpower with the brakes.
 

sunjack

Member
Apr 20, 2021
28
2
Shanghai, China
By the way, has anyone seen any reliable information about the road/weather conditions at the time of the collision? I don't recall reading anything about that but I might have missed it in all the noise.
As far as I remember, the reported weather condition is good. There was no snow or rain. But I do remember reading somewhere, some driver familiar with the road said that there are construction trucks hauling sand or soil around, which could leak some of its load during transportation. It could be the reason the ABS was triggered before collision.
 

Tam

Well-Known Member
Nov 25, 2012
8,778
7,602
Visalia, CA
...The two pedal mode is there because this is almost a necessity in hilly areas for a lot of drivers...
The above statement confirms that driving with 2 feet on both pedals is possible with a Tesla and it is not impossible.
I think the point however of the comment you were responding to is that the power is so low in 2 pedal it's trivial to overpower with the brakes.

It is true that Tesla brakes override the accelerator. I can FLOOR both the brake and accelerator pedals and the car will stop.

But that does not mean it's impossible to drive a Tesla with the 2 feet method. With the 2 feet method, I just might have to apply the brakes 40 times per 30 minutes instead of just using 1 foot to ease up the accelerator.
 
Last edited:

sunjack

Member
Apr 20, 2021
28
2
Shanghai, China
It's more like driving with 2 feet and not 1 foot.

The press reports that the 30-minute log shows the driver drove at a high speed above 100 km (62MPH) and applied the brakes more than 40 times.
The accident happened in a "national highway" in China, which is not like US highway. There are traffic lights a few miles apart, truck/semi driving at 40-50 mph (sometimes in the left lane). Cars want to move fast would need to maneuver in traffic. I would not be surprised the driver brakes more than 40 times in 30-minute log, if he is a aggresive driver.
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top