Track test: How does brake-override affect enthusiast driving?

Some driving enthusiasts are griping that " smart throttle" or "brake-override" technology, intended to halt dangerous sudden-acceleration events, will take the fun out of driving. Not to worry. We've just run some tests that prove that the thrill isn't gone.

Brake override is a software algorithm that gives the brakes precedence over the throttle if both are activated at once. Toyota, plagued by reports of sudden-acceleration problems and now undertaking massive recalls, has pledged to implement this feature in all future models and to retrofit it in some of the recalled vehicles. It's already widely used by Chrysler, Mercedes-Benz, Nissan/Infiniti, Volkswagen/Audi, and on some GM models.
  Despite some concerns, brake override doesn't impede a boy racer from using fancy footwork like heel-and-toe downshifting or left-foot braking to tease a car through fast turns or from pulling off those crowd-pleasing, tire-smoking, "brake stand" burnouts. Nor does it prevent a regular driver from using the brake and gas pedal together to start off on a hill.

Here's what we did: At our track we set up some challenging driving situations and used three of our test cars that came equipped with brake-override technology: a Mercedes-Benz E350 and a Volkswagen Jetta Sportwagen with automatic transmissions, and a manual-shift Volkswagen GTI.

Heel and toe: Driving the sporty GTI, we zipped through our serpentine handling course using the heel-and-toe technique to rapidly downshift, blipping the throttle while braking before each corner. The engine revved just as expected and desired.

Trail braking: A practiced driver can sometimes take corners faster in a front-wheel-drive car by using brakes and throttle simultaneously. In an autocross simulation, we could power our GTI through the turns just fine while lightly applying the brakes.

Hill starts: If you have to start off when part way up a steep hill, say when stopped for a traffic light, you normally hold the car with the brake while easing down on the gas pedal. The Jetta and the Mercedes E350 executed this start-off with ease, as did our 2010 Toyota Camry, which had brake-override installed during a recent recall service. 

Brake stand: Brake-override doesn't even bar drivers from spinning the rear wheels, if they want to. Using our Mercedes E350 with its traction control switched off, we sat on the brakes and kicked down the accelerator. As you'll see from the picture, we could still smoke the tires. Of course we would never, ever, do this except in the name of science.

What did we prove? We performed these demonstrations not just to set race drivers' minds at ease but to undo a fundamental misconception. Brake-override doesn't cut all power to the engine when you hit the brakes. It reduces power enough that hard braking will always easily stop the car even if for some reason--any reason--the throttle mechanism is stuck open.

We think it should be mandatory in every car. It's not a cure-all, but it is an easy-to-adopt safety measure that should halt a runaway car using brakes alone, whether that event is caused by a jammed gas pedal, a stuck linkage, an electrical fault, or by some driver errors. (But, of course, brake-override won't help if the unintended acceleration is caused by someone flooring the accelerator instead of using the brake.)   

Read: "Consumers Union calls for changes to strengthen U.S. car-safety net."

—Jake Fisher and Gordon Hard

Be sure to follow Consumer Reports Cars blog (RSS) and Twitter (@CRcars) to keep up with the latest information and advice, also see our unintended acceleration guide.

Related:
Consumers Union calls for changes to strengthen U.S. car-safety net
Toyota reportedly worked with feds to save $100 million in recalls
Eight things that can dramatically improve auto safety
Five key fixes automakers should make now to reduce unintended acceleration
Unintended acceleration stories wanted
How to tell if your Toyota is affected by the recent recalls
How to stop a runaway car: Don't pump the brakes