There are news stories from northwest Minnesota about a state trooper who was able to stop a runaway 2022 Honda Pilot driven by a teenager.
According to the stories, the teen wasn’t able to use his brakes or the emergency brakes, shift into neutral, or turn off the engine, as the car accelerated to 113 MPH. Those are the things we were taught to do about stopping a runaway car in driver’s ed, but that was before everything was computerized.
I would think that some of these systems would not be connected to the others, like the brakes and ignition. So what’s happening here? Did the car’s computers go crazy, or is this user’s error. (The article is actually from October 1st 2024.)
There aren’t any details but usually the driver just tries to slow down a bit by applying the brakes on and off or just pressing normally. This will quickly heat the brakes up. You have to just press the brake pedal HARD. The car will stop. I’ve been there and also demonstrated it to a girlfriend once. In a safe spot I reached over with my left foot and pressed the gas then had her use the brakes. It is scary towards the end when the rear wheels keep trying to spin. With a front wheel drive car that wouldn’t happen as much as the front brakes are more powerful.
When it happened to me on a BMW the throttle shaft rotated and clipped over a hose clamp that was slightly in the wrong orientation. I had just passed a truck on a secondary road and was at full acceleration. I braked hard and found a spot to pull over. The truck driver was not happy.
The Pilot has a push-button shifter. I’d assume that you can always put it into neutral but I’m not certain.
It may have been something like an aftermarket floormat holding down the accelerator. Like mixdenny said, if you ride the brakes, say, out of confusion and panic while the accelerator is being held down by the mat, then the brakes can overheat and become ineffective. This would take several minutes of panic braking/accelerating but it’s plausible. Than maybe he tried to put it into park because 18 year olds don’t understand what neutral is.
Some automakers implemented a safety feature starting about a decade ago that cuts the throttle if the brake is applied, to prevent these types of events. But that’s far from universal.
Long story short, these events are all most lilely gas pedals being physically stuck on something combined with a healthy dose of panic. There’s scant evidence that computerized cars have had multiple simultaneous systems failures that result in runaway acceleration despite rational, calm actions from the driver.
I read once the problem with runaway trucks on hills, and likely with this vehicle - brake fluid will absorb water over time if not maintained properly. When the brakes overheat, the water in the brake fluid may boil and become gas. Hydraulic brakes rely on the incompressibility of liquid to ensure the pressure on the pedal produces pressure on the brake pads. Air or vapour in the line means the pressure is not as strong.
I would be very concerned about electronic systems without a hard switch - but I guess there are more and more of them in our lives.
The article says the driver tried to put it in neutral, but could not. It doesn’t say he tried to put it in Park.
I looked at the owner manual for a 2022 Honda Pilot (PDF file here). Page 535 says that if you’re in R, N, D, or S (paddle-shifter mode), and you try to change to “P” while the car is moving, the transmission will shift into “N”. The owner manual doesn’t say what happens if you try to put it in “N” while moving…so maybe nothing happens? That would be consistent with the article.
Page 523 says you can turn the engine off when the vehicle is completely stopped, which seems to imply that you can’t shut the engine off while the vehicle is moving. If so, that seems like a major safety flaw. Regardless of the reason for out-of-control acceleration - throttle glitch, floor mat wadded up on the accelerator pedal, whatever - there should be a way for the driver to cut power without being required to first bring the vehicle to a dead stop.
Big-rigs utilize air brakes. Boiling the brake fluid (whether wet or dry) isn’t a problem for them. Instead, over heating the brakes causes brake fade: temperatures get so high that the coefficient of friction between the brake pads and the rotors/drums goes down. At that point, you can press the pedal as hard as you want and you will no longer get the braking you need. Engine braking is a must for big trucks descending long/steep grades.
Note that for vehicles with hydraulic brakes, it’s possible to boil brake fluid even if it’s brand new and moisture-free. The vehicle in the OP’s article was a 2022 Honda Pilot, so only a couple of years old; its brake fluid should have been in fine shape.
The uncomfortable thing about all of these unintended acceleration cases is that, at some point, investigators have to come out and call the victim, someone who just experience a traumatic event (and in some cases lost their life), a liar. And then they have to come up with plausible explanations for why the user thought they were doing something that they weren’t.
It’s interesting that it should have gone into neutral even if he tried to put it into park. The question now is, why didn’t it go into neutral? They’ll be able to test the car now to see if there’s some problem with the transmission, and if there’s not…
The article didn’t say he tried to put it in park, it says he tried to put it in neutral. The owner manual doesn’t say what happens if you try to put it in neutral while moving. It’s entirely possible he really was pushing “N” with no effect.
I know, I was speculating, like the investigators will be. Cars without push-button shifters can’t be put into park while moving, so I thought maybe he got confused about which button he was pushing (it’s naturally to try to put cars into P but most people with push-button shifters will never use the N button) and the car wouldn’t respond. But as you say, that’s not how this particular car works.
If what you’ve quoted is correct, and I have no reason to doubt it, then this theory is irrelevant and I’ve got nothing. Just that the DBW system and the transmission controller are completely separate systems and it doesn’t seem likely that there would be failures in both at the same time.
What I am worried in modern cars is that as we moved from mechanical to electronic interfaces, this could happen due to a computer malfunction and when you try the old standbys like hitting the brakes, putting it in neutral, &c. the car’s response is in effect, “I can’t do that, Dave.”
Thanks for the replies so far. The part that I’m not understanding is despite the teen driver claiming to not be able to brake, use the emergency brake, shift into neutral, or turn off the engine, the trooper was able to get the car to stop by positioning his car in front and telling the driver to contact the trooper’s car bumper while the trooper braked.
If the Honda was so uncontrollable, why was the trooper able to get the Honda to stop by braking in front of it. You’d think the tires would still be spinning, even if stopped. How?
After thinking about it, it sounds like the teen driver just totally panicked. Or was caught speeding and had to come up with an excuse why he didn’t stop or slow down earlier. I wonder if his car got looked at by Honda; they should be very interested in this incident.
Yet another reason why manuals are better. If the accelerator sticks or the brakes fail you can simply grab the stick and pull it out of gear or just step on the clutch pedal.
Yes, I did just use this event as a chance to hype manual transmission cars, which are obviously superior. But I was able to do it with facts, so win-win.
Probably many (most?) cases of unintended acceleration are user error or deliberate attention-seeking. However there is often no way of knowing exactly what happened or reproducing it, so it’s difficult to rule out car malfunction.
If the car’s accelerator pedal is defective electrically and the computer falsely thinks that the accelerator is floored, the car will accelerate. The car’s diagnostics tools may later “confirm” that the pedal was floored during the whole incident, but really that just says that the computer saw a depressed pedal. You’d better hope that the electrical defect can be detected separately after the fact, otherwise the driver will just be called a liar.
(Not related to Honda Pilot, or to braking:) Here is an article about an engineer who investigated the ECM firmware used by Toyota and its possible role in unintended acceleration.
Healthy brakes will always defeat an engine. If the kid couldn’t stop the Pilot, it was because either he was too timid to brake hard, or he had roasted/destroyed the brakes by keeping the brakes applied heavily without getting the car completely stopped.
The Pilot has a 3.5L engine, 280 horsepower. It’s plenty big, but it’s not stupid-big. When the trooper gets in front, he gets off the gas and gets on the brakes; now his brakes are trying to slow the mass of two cars, but they’re only fighting the engine in the Pilot. The trooper stands on his brake pedal, and stays on it until they both come to a stop. End of drama.
As far as spinning tires, the Pilot is a fat pig of an SUV: about 4300 pounds. A 3.5L engine is not gonna spin those tires, even in first gear.
To be fair, people do strange things when they panic.
I recall an analysis of an industrial accident where I used to work, the person watching the other person in life-threatening distress (he died) ran past half a dozen people who could have helped, to find his supervisor to get help. The brain does funny things in a panic.