What is Brake Assist, and How Does it Work?

Emergency brake assist helps out with additional braking force

An illustration of emergency brake assist in action.

Wikimedia Commons / Ryan Stubbs / CC BY / Emergency brake assistance overlay added

Brake assist is a safety feature that is designed to help drivers apply the right amount of force to their brakes during panic stop situations. When a driver fails to apply the maximum amount of force to their brake pedal during an emergency situation, brake assist kicks in and applies more force. This results in the vehicle stopping in a shorter distance than it would have without brake assist, which can effectively prevent collisions.

Terms like “emergency brake assist” (EBA), “brake assist” (BA), “automatic emergency brake” (AEB), and “auto brake,” as in Volkswagen’s Collision Warning with Auto Brake (CWAB), all refer to similar brake assist systems that are designed to augment braking power in the event that a driver fails to apply enough pressure to the brake pedal during a panic stop.

Despite the variety of different names, all brake assist systems operate under the same basic principles and result in additional stopping power.

When Is Brake Assist Used?

Brake assist is a passive safety technology, so the driver doesn't have to worry about using it. These systems automatically kick in whenever extra brake force might be necessary to prevent an accident.

Some situations where brake assist might activate include:

  • A child or animal suddenly runs into the road, forcing an emergency stop.
  • When a curve in the road, or a hill, obstructs the driver's view of the road ahead, and the driver suddenly comes upon an accident or stopped traffic and is forced to stop immediately.
  • Another vehicle swerves into the driver's lane and either slows down or stops, forcing an immediate reduction in speed to prevent an accident.
  • Debris or large objects fall from an unsecured load into the roadway, forcing the driver to stop or swerve dangerously into another lane.

How Does This Technology Work?

Brake assist systems typically kick in when a driver applies their brakes suddenly and with a great deal of force. Some of these systems are able to learn and adapt to a particular driver's braking style, while others use pre-set thresholds to determine when assistance is needed.

When a brake assist system determines that a panic or emergency stop situation is underway, additional force is added to the force that the driver has applied to the brake pedal.

The basic idea is that the brake assist system applies the maximum amount of force to the brakes that can be applied safely in order to bring the vehicle to a stop within a minimum amount of time and distance traveled.

A diagram illustrating how emergency brake assist works.
Jeremy Laukkonen

Since the driver is effectively taken out of the loop when a brake assist system kicks in, the EBA and anti-lock brake (ABS) technologies are able to work together to either stop the vehicle, and prevent a collision, or slow it down as much as possible before a collision occurs.

In a situation like this, the brake assist system will continue to apply the full amount of available brake force, and the ABS will kick in to pulse the brakes in order to prevent the wheels from locking up.

How to Use Emergency Brake Assist

  1. Apply the amount of force to the brake pedal that you believe is necessary.

  2. If equipped with emergency brake assist, the system will calculate the expected stopping distance, and the distance to any obstructions in front of you.

  3. If necessary, the emergency brake assist system will automatically apply additional force to the brakes.

  4. Keep consistent pressure on your brake pedal, and maintain control of the vehicle. Do not let go of the steering wheel.

  5. If there was sufficient distance for your vehicle to stop with an appropriate level of brake force applied, your vehicle will come to a stop before impacting the vehicle or other obstruction in front of you.

  6. If there was not sufficient distance, your vehicle will collide with the object in front of you. However, it will do so with less force than it would have without the emergency brake assist feature.

Is Emergency Brake Assist Necessary?

Without emergency brake assist, many drivers fail to fully appreciate exactly how much force is needed during a panic stop situation, which can lead to avoidable accidents. In fact, one study showed that only about 10 percent of drivers apply a sufficient amount of force to their brakes during panic stop situations.

Additionally, some drivers aren’t aware of the best way to make use of ABS.

Prior to the introduction of ABS, most drivers learned to pump the brakes during a panic stop, which effectively increases stopping distance but helps prevent the wheels from locking up. With ABS, however, pumping the brakes is unnecessary.

When full brake force is applied during a panic stop, the pedal will buzz or vibrate as the ABS pulses the brakes much faster than the pedal could be pumped otherwise. If a driver is unfamiliar with this feeling, he may even back off of the pedal, which will further increase the stopping distance.

Since emergency brake assist takes over before that occurs, a vehicle equipped with this technology will continue to slow down even if the driver fails to continue braking.

If you’re familiar with the way your vehicle operates during a panic stop, then emergency brake assist isn’t really necessary.

For the other 90 percent of us, practicing panic stops can also remove the need for an emergency brake assist system. However, while practicing panic stops can lead to safer driving, it’s vital to only perform such a maneuver in an area where there are no vehicles, pedestrians, or other things that you might hit.

The History of Emergency Brake Assist

Automakers regularly perform a variety of tests on their vehicles to determine strengths, weaknesses, safety characteristics, and other factors. In 1992, Daimler-Benz performed a study that revealed some striking data about simulated panic stops and crashes. In this study, more than 90 percent of the drivers failed to apply enough pressure to the brakes when faced with such situations.

Armed with data from their driving simulator tests, Daimler-Benz partnered with the aftermarket parts company TRW to create the first emergency brake assist system. The technology was first available for the 1996 model year, and a number of other automakers have subsequently introduced similar systems.

TRW, after absorbing LucasVarity in the late 1990s, acquisition by Northropp Grumman in 2002, and subsequent sale to an investment group as TRW Automotive, continues to design and produce brake assist systems for a variety of automakers.

Who Offers Emergency Brake Assist?

Daimler-Benz introduced the first emergency brake assist system in the late 1990s, and they continue to use the technology.

Volvo, BMW, Mazda, and a variety of other automakers also offer their own take on brake assist technology.

Some of these technologies “pre-charge” the brakes so that full braking force can be applied during a panic stop regardless of how hard the driver presses on the brake pedal.

If you’re interested in emergency brake assist, then you might consider asking at the dealership of your choice whether any of their models include a similar technology.

What Alternative Technologies Exist?

Emergency brake assist is a relatively simple technology, and a lot of automakers build it into significantly more complex car safety technology systems.

One similar technology is automatic braking, which uses a variety of sensors to apply the brakes before an accident can occur. These systems kick in regardless of driver input, and most of them are designed to reduce the severity of a collision when an impact is unavoidable.