How to stop a runaway car: Don’t pump the brakes

Despite a massive recall by Toyota of 3.8 million vehicles to address sudden runaway acceleration, National Highway Traffic Safety Administration (NHTSA) is still investigating the exact cause of this problem. They are concerned that the accelerator pedal getting stuck by the floor mat – the purpose of the recall - is not the exclusive cause, according to the New York Times.

Whatever the cause of unintended acceleration, the best defense is to know how to safely regain control of the car should it happen to you. In a previous post, we wrote that putting a car in Neutral might save your life. Our latest tests show that pumping the brakes at full throttle can make a bad problem even worse, as demonstrated this video from ABC News. (See the report "Owners of Toyota cars in rebellion over series of accidents caused by sudden acceleration" at ABCNews.com.) 

A NHTSA report released this week points out that some drivers can “react by applying the brake pedal multiple times, depleting the braking system’s (vacuum based) power assist.
 
Testing theory at the track
We decided to find out just how quickly you could lose power brakes with a stuck throttle. Using our test track and several test vehicles, we accelerated to 60 mph and hit the brakes with the accelerator still floored. Once the brakes were applied, the vehicles began fighting us. The transmissions downshifted trying to maintain speed.
 
Instead of holding the brakes, we tried pumping them. This test confirmed that pumping the brakes is a really bad strategy. Power brakes rely on engine vacuum to provide additional brake pressure. At full throttle, the engine doesn’t generate any vacuum. So as soon as we removed and reapplied pressure to the brake pedal, the power assist disappeared and stopping the car became hopeless. “There was no way I could push hard enough on the brakes to slow the car down when the engine was fighting me,” said Sr. Automotive Engineer Jake Fisher.
 
Bottom line
The best strategy to stop a runaway car is to press and hold the brakes and shift into neutral. Modern cars have rev limiters, which will protect the engine from over-revving. Even if your car doesn’t, don’t worry about your engine’s life—worry about your own.

 —Eric Evarts

Related:
Gas-pedal inspection shows most do not pivot
More than floor mats: NHTSA report gives more details on Lexus crash
Putting a car in Neutral might save your life
Putting stuck floor mat survival strategies to the test
Floor mat survey reveals problem with all-weather mats
Toyota and Lexus floor mat recall is official
Toyota advises 3.8 million Lexus and Toyota owners to remove floor mats
Misaligned floor mat may have caused calamity

Comments

[John]

Why don't all cars allow the brakes to override the gas? leave it to the Germans to design these safety extras into even a VW. I own both an Audi and a Toyota, Audi has put hundreds of extras most will never know about but when you need things like the brake overruling the accelerator.
I had no idea a Toyota Camry engine could over power the brake system, with drive-by-wire systems in most modern cars the gas pedal in these cars is nothing but a switch with a wire harness, if the signal from this switch or anything from the harness to a failure in the computer system causes the throttle to open up wide I find it hard to imagine the brake system in these cars don't have a fail safe throttle over ride designed to cancel a throttle wide open signal with the brake pedal applied.

[Oldsmoboi]

Back in the day, gas pedals were hinged to the floor. There was no way to get the pedal stuck under the floormat.

Interesting thing about that vacuum assist.

Random obscure trivia: I had a 1985 Continental that had hydraulic assist brakes. Rather than relying on engine vacuum, the power steering pump also provided hydraulic assist to the brake master cylinder.

It was annoyingly more expensive when the power steering pump went out, but now it sounds like it was safer setup.

[bob campbell]

Lexus has a big problem. The driver of this vehicle was a California Highway Patrol Officer. The news from KFI radio says that the brakes were ground down to bare metal and that he would have had to hold the start button for 3 seconds to shut down the engine. At a speed of 120 mph it appears to be difficult to find neutral or to stop this vehicle!

[Bence]

I owned a Jaguar with floor hinged gas pedal. Yet a similar problem occurred when I did a kickdown. The mat slid forward and kept the gas on the floor. It was funny and it looked great from the outside (drifting in a gas station), but for inexperienced drivers it was a dangerous situation. I switched the car off and that was it.
HOWEVER, as much I feel sorry for the CHPO family, it takes a considerable time to call 911 and the Lexus to take the 120 mph speed. During these agonizingly long MINUTES (as you can't wear down brake pads in seconds, call 911, waiting for a solution, etc.), FOUR people are unable to figure out that you need a half inch nudge to put the tranny selector from D to N...??? With a CHPO "driving"??? Seriously???

Well, that's NOT Toyota's problem!!! And BTW, I love to do a little performance driving (especially in the snow) where you need the gas/brake simultaneously to stabilize the car. If you try it in for example a *fine* German masterpiece, you'll quickly find out that it is maddeningly impossible.

[William LeGro]

Our 2010 Prius, and many other cars, have electric brakes. Does the warning against pumping the brakes apply to electric brakes? Does vacuum assist exist with such brakes?

And can the Prius be shifted into neutral at speed? I don't want to test it without knowing this first, though of course I would in an emergency.

[Terrance]

I was unaware until this report that now the computer controls the gasoline flow rather than the accelerator pedal. What else does the magic computer do? Can CU provide a block diagram showing what the inputs and outputs to the on-board computer are?

[genesii]

I too, am old enough to remember floor hinged accelerator pedals as well as floor mounted headlight dimmers.

The floor mounted pedal is not the answer. In the Northeast, during the winter, both the floor mounted dimmer and the pedal were subjected to melting snow and salt leaving the dimmer unusable on many occasions and the accelerator pedal sticky too many times.

[Bobbie Jones]

Other than the VW Jetta, what other German cars
have the system that allows the brake peddle to overide
the gas peddle in sudden acceleration events?

[Gabriel D Kim]

I had a VW Passat. It had the similar problem. It had a flimsy floor mat, and got stuck between gas pedal and floor. One time, it accelerated so fast, it crashed on to the vehicle in front. It happened so many times, I threw away the mat.

[l h butterworth]

What's the matter with simply turning the key to off?

(That was what my dad taught me to do when he taught me how to drive back in the 50's).

[David Isenbergh]

In response to I. H. Butterworth's post: With a modern car, if you turn off the ignition while driving, the steering wheel is likely to lock. You don't want to be on the highway without being able to turn.

[Kyle]

@ John,

"Leave it to the Germans to design these safety features into even a VW".

I've owned a VW new beetle, and many Toyota vehicles, and can say that while the Volkswagens often have "superior engineering" or more "advanced features'", what are the odds they will actually WORK when you need them? Volkswagen has been plagued with shoddy reliability for the past two decades. It's one thing to incorporate good ideas into a vehicle. It's another thing to make sure they actually will work when needed. It will take a decade of Excellent Ratings from CR before I even walk into a VW dealership again.

[aussie1]

in responce to David Isenbergh if you only turn the key one notch all u lose is hydrolic presure casing a loss of power streering not a streeringlock i know this becaue i go down hills with my car turned off