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How Brake Assist Works


Providing Power for Panicked Stops
Brake Assist can help sleepy nighttime drivers react properly when sudden danger arises.
Brake Assist can help sleepy nighttime drivers react properly when sudden danger arises.
Matt Cardy/Getty Images News

Let's go through another brake assist-aided stop. This time, we'll tackle it step by step.

You're traveling down a deserted country road on a moonless night, with the forest seemingly closing in on either side. Your high beams throw off barely enough light for you to comfortably drive the speed limit. Suddenly, a family of deer comes loping onto the pavement a few hundred feet ahead.

As your foot instinctively clamps down on the brake pedal, a sensor immediately knows, by the speed and pressure of your foot on the pedal, that this is an emergency. Within a fraction of a second, the brake assist system signals the brakes to direct maximum clamping power to the brake calipers. The pedal pulses as its anti-lock braking system (ABS) kicks in, working in concert with the brake assist. The vehicle remains under control as it decelerates and stops far short of the crossing deer. No animals are harmed - - and your insurance premium escapes equally unscathed.

There's more than one type of brake assist. Volvo offers the City Safety system, which automatically brakes in urban stop-and-go traffic [source: Volvo]. Mercedes-Benz came up with an additional feature known as Distronic Plus. Toyota has developed a system that combines a vehicle's brake assist system with navigation data, so that the brake assist engages during panicked stops at traffic signals [source: Toyota].

Active Brake Assist is a newer technological development that loads the brakes with hydraulic pressure milliseconds before an impending crash. This helps deliver more stopping power to the brakes even sooner. Bosch, the German parts supplier, calls its version Predictive Brake Assist. It's designed to communicate with the vehicle's Adaptive Cruise Control radar sensor to recognize situations that could develop into an accident. Beyond a certain triggering threshold, the system applies light brake pressure that the driver won't even notice as it prepares the vehicle to stop suddenly. Beyond another threshold of proximity, the system activates the full brake assist mechanism.

Why is all this necessary? Are drivers just that slow to react on the road? Bosch explains this innovation as necessary because, "even in critical situations, only about a third of drivers react appropriately and hit the brakes hard enough." As a result, the company adds, "the hydraulic brake-assist system is not triggered" [source: Robert Bosch GmBH].

Does brake assist actually make driving safer? Go to the next page to find out.


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