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

Brake assist is a safety feature designed to help drivers apply the right amount of brake force during panic stops. 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 without brake assist, which may prevent collisions.

Terms like “emergency brake assist” (EBA), “brake assist” (BA), “automatic emergency brake” (AEB), and “auto brake,” all refer to systems that are designed to augment braking power if a driver fails to apply enough pressure to the brake pedal.

Despite the 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, meaning the driver does not actively apply it. These systems automatically kick in whenever extra brake force is deemed 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 hill, foggy weather, or a curve in the road obstructs the driver's view of an accident or stopped traffic, forcing a sudden brake stop.
  • Another vehicle swerves into the driver's lane and either slows down or stops, forcing the driver to slam the brakes.
  • Debris or large objects tumble into the roadway, forcing the driver to stop or swerve dangerously into another lane.

How Does Brake Assist Work?

Brake assist kicks 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 already applied. The idea is that the brake assist system applies the maximum amount of force to the brakes 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.

If there is sufficient distance for a vehicle to stop with an appropriate level of brake force, the vehicle will come to a stop before impacting an approaching vehicle or obstruction. If there is not sufficient distance, the vehicle will collide with the object. 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, drivers often fail to appreciate how much force is needed during a panic stop situation, which can lead to accidents. In fact, one study showed only about 10 percent of drivers applied sufficient 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 otherwise be pumped. 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. But for most people, practicing panic stops may limit 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 objects in the road.

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 the study, more than 90 percent of 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 since introduced similar systems.

TRW continues to design and produce brake assist systems for a variety of automakers.

Who Offers Emergency Brake Assist?

Daimler-Benz (now Daimler AG) 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.

Consider asking dealers which, if any of their models include brake assist or similar technologies.

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 such tech 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.