With a large test track and a fleet of vehicles at their disposal, the magazine's engineers initially focused on the "just step hard on the brakes" method of bringing the car to a halt. Interestingly enough, CR tested a Mercedes-Benz E350 and a Volkswagen Jetta Wagon – both fitted with drive-by-wire "smart throttles" that are designed to ignore conflicting inputs (throttle and brake at the same time). CR reports that these cars simply shut down to idle and came safety to a stop. The story was a bit different with a Toyota Venza and Chevrolet HHR, however. When the brakes on those vehicles were firmly applied at 20 mph, their transmissions downshifted to fight the deceleration. The vehicles were both eventually brought to a stop after the first test. However, when the test was repeated at 60 mph on brakes that had been cooled since the earlier run, both vehicles quickly suffered fade from their overheated brakes and were unable to come to a complete stop.
As is the general rule, a vehicle's braking system is stronger than the engine when the car is standing still. However, the tests conducted by Consumer Reports demonstrate that the power of the engine combined with the momentum of a car at highway speed is often enough to overtax the braking system's ability to bring the car to a stop (the brakes overheat and fade). Their suggestion is to simply slide the transmission lever to neutral – removing the engine's power from the equation – and apply the brakes firmly to bring the car to a stop. Once stopped, shut the engine off and then shift safely into Park. This "shift-to-neutral" action was equally effective on all four vehicles. The CR team also explored shutting off the engine (turn the key or hold the Start/Stop button down for more than a few seconds). This method also worked well, but it does present some danger. Switching off the engine disables power steering on most vehicles, eliminates brake boost, and may lock the steering wheel if the key is turned back too far – making a safe stop nearly impossible.
[Source: Consumer Reports | Image: George Heyer/Getty]]