Recent reports of stuck accelerator pedals causing crashes and Toyota’s enormous recall has caused many to question whether or not a vehicle’s brakes are powerful enough to overpower the engine to stop a vehicle, and what you should do if you are ever in that situation. Most experts agree that a typical production car engine won’t overpower the car’s brakes from a stop. But what happens at speed is another question. Since we just happen to have a test track and a few dozen test cars at our disposal, our automotive engineers decided to play MythBusters and put it to a test.
 
Our first two subjects were the Mercedes-Benz E350 and Volkswagen Jetta Wagon, German cars with so-called “smart-throttle” technology. Both will electronically ignore the throttle input if the brake pedal is depressed. With both, we accelerated to 60 mph and then hit the brakes with the throttle pedal still planted to simulate a condition where the floor mat might have stuck it in place. With both vehicles, we were able to safely slow to a stop despite the engine having been at wide-open throttle. After stopping, the engines idled even with the throttle pedal still floored.
 
Verdict: The Mercedes and Volkswagen Smart-Throttle technology works.
 
Next up, we tried our Toyota Venza and Chevrolet HHR. Since these lacked smart-throttles, we proceeded more cautiously. So we decided to start this test by flooring the cars to 20 mph (instead of 60) and then slamming on the brakes. While we stopped both cars, the transmissions downshifted hard, trying to fight us on the way down, and we needed to exert quite a bit of brake pedal effort to stop completely. We then drove a lap around our test course to cool the brakes and repeated the procedure. This time we accelerated to 60 mph before we slammed on the brakes. Again, the engines downshifted and fought us all the way down. But by the time we slowed down to about 10 mph, the brakes had faded so much that we weren’t able to come to a complete stop.  If the driver had less strength or was traveling at higher speeds, they would not be able to slow down nearly as much.
 
Verdict: Most people will likely have a tough time stopping a car using the brakes with a stuck throttle without a smart throttle.

So what should you do if you are put in such a situation? The answer is simple: Put the car in neutral. In each one of the cars we tested, we were able to easily nudge the gear lever into neutral and stop the car quickly. All modern engines have rev limiters that prevent the engine from over revving and damaging the engine. You can safely shut off the engine after you come to a stop. However, we do not advise shutting off the engine while still driving. We tried this with our Toyota Venza—as Toyota suggests—by holding down the start/stop button for three seconds. While this also allowed us to stop, we lost power steering and had trouble maneuvering the vehicle due to the extremely heavy steering.

Related:
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

—Jake Fisher, photo by Mike Leung.