Forward Collision Mitigation (Auto-Braking) Systems

Forward Collision Mitigation Systems Ratings

What Is It?

Forward Collision Mitigation (FCM) systems detect how far and fast the vehicle in front of you may be moving, and automatically apply the brakes if you do not respond. In this way, FCM systems work to reduce the chance of crashes, and reduce the severity of collisions when they do occur. FCM should not be confused with Forward Collision Warning (FCW). A Mitigation system will both warn the driver and slow the vehicle, whereas a Warning system will only warn the driver.

Why Did FCM Earn a 5-Open and 3-Solid Star Rating for Rear-End Collision Prevention?

Recently released test track data shows that FCM systems in certain scenarios are able to avoid or mitigate front-to-rear crashes greater than 80 percent of the time. This qualifies for a top open-star rating. Insurance data from equivalent Volvo models with and without FCM found a 23% crash reduction for the equipped vehicles, yielding a 3-Solid Star rating.

Why Did FCM Earn a 3-Open and 2-Solid Star Overall Safety Benefit Rating?

The 23% crash reduction reported in the insurance data translates to a 6.6% reduction in crashes overall, based on the proportion of crashes accounted for by rear-end collisions. This qualifies for a 2-Solid Star rating. Larger theoretical estimates based on other studies yield a 3-Open Star rating.

Why Would I Use This Technology?

Forward collision crashes, in which the front of a vehicle collides with another vehicle on the road, are very common, accounting for up to a quarter of all crashes. FCM systems detect when the vehicle may be about to collide with another object, and automatically slow the vehicle. The primary benefit of this technology is that it alerts drivers to dangerous situations and takes pre-emptive action to avoid a crash.

What Do Drivers Think?

A recent survey showed that only about 24% of respondents were aware of FCM technology. Of those, 60% said the technology was easy to use, and 47% considered it to be useful. A study that asked about drivers’ satisfaction with FCM found that drivers were moderately satisfied with it. Drivers who experienced a “false braking event,” in which the system detects a crash that isn’t happening and stops the vehicle, tend to have a lower opinion of these systems.

How Well Does It Work?

The Insurance Institute for Highway Safety estimates that these systems could reduce crashes by up to 20%, preventing 66,000 serious crashes and 879 fatal crashes per year.

Who Benefits Most?

FCM systems would be most useful for inattentive drivers who have trouble monitoring their surroundings at all times. It would also be especially helpful to drivers who have trouble reacting quickly to unexpected events, such as older drivers or those with disabilities. Additionally, FCM may be particularly relevant to drivers who spend a great deal of time in stop-and-go traffic, such as commuters in congested urban areas.

In What Situations Doesn’t It Work?

Camera-based FCM systems are less effective than radar-based systems, as these do not work as well at night and can be “blinded” by sunrise and sunset glare. Additionally, some systems will only detect other moving vehicles or vehicles traveling at a minimum speed, while others will detect both moving and stationary vehicles. As always, it is vital for the driver to remain vigilant, and not become too reliant on the system for assistance.

Mobility Significance

FCM would be especially helpful for drivers who react more slowly to their surroundings, whether due to age or disability.

Not All Systems Are Alike

FCM systems may be camera-based or radar-based, and have different weaknesses as a result (see “In What Situations Doesn’t It Work?”). In addition, not all systems are capable of detecting stationary vehicles, or slowing the vehicle at the same rate.

Different Names, Same Idea

FCM can be found under a number of different names, including:
•    Crash Imminent Brake (CIB)
•    Autonomous Emergency Braking (AEB)
•    Emergency Brake Assist (EBA)
•    Predictive Brake Assist (PBA)
•    Pre-crash warning and braking systems (PCWBS)

How Can I Learn More?

Full references to all studies quoted above can be found in the official AAA Foundation report, "Evaluating Technologies Relevant to the Enhancement of Driver Safety." The project's Fact Sheet provides more detail on the rating system itself, and the criteria used to assign solid and open stars, both for Overall and Scenario Specific ratings.