With statistics like that, it may be worthwhile getting this feature on your next car. But, we think that you need to know more. In this Car Safety Guide, we help you to understand forward collision warning (FCW) and its complementary technology, Automatic Emergency Braking (AEB), to help you weigh these options in your next car purchase.

What Are Forward Collision Warning and Automatic Emergency Braking Systems?

Broadly, an FCW system monitors the vehicle’s speed, as well as the speed of the vehicle in front of it, while measuring the distance between the two vehicles. If the vehicles get too close the FCW system will use a variety of warning devices, primarily auditory, to warn the driver of a possible impending crash. The FCW is considered a driver assistance system. It alerts the driver to act but generally does not take control of the vehicle.

AEB systems are often packaged with FCW systems. While the FCW portion alerts the driver to an impending collision, the AEB will act to either initiate braking (called Crash Imminent Braking, CIB) or help the driver brake harder (called Dynamic Brake Support, DBS). Keep in mind that AEB systems’ design is highly dependent on the speed the car is traveling. Common terms are ‘city-speed’ for lower speed systems, and ‘highway-speed’ for systems designed for higher speeds.

What Questions to Ask?

If you are considering a car with FCW or AEB systems, then it is worthwhile knowing something about how the systems were designed to work. For example, if an AEB system was only qualified at low speeds (e.g., less than 25 mph), it is unlikely to provide much protection while driving at high speed on the freeway (say, at 55+ mph).

Since the systems made by each manufacturer (and even amongst models within the same manufacturer!) often have different design features and terminology, it is useful to ask questions about the systems prior to making your purchasing decision. Here are some questions to ask:

1. Is the system designed to activate at low speeds or high speeds?
2. What type of warning is provided? Audible (like beeping), visible (like flashing lights), or haptic (like a vibration)?
3. What kind of AEB system is it? CIB (initiates braking if the driver hasn’t)? Or DBS (helps the driver brake harder)?
4. How does the system suit your style of driving? Research shows that 93-99% of drivers keep their FCW system active, drivers who tend to tailgate may not like it.

FCW, AEB, and AUTO GRADES

An Auto Grade tells us how well or how poorly a car has protected its drivers in the worst crashes. In other words, Auto Grades are based on the track record of protection when a crash occurred.

FCW and AEB systems are part of the general category of “driver assist” technologies. These technologies are intended to help drivers prevent crashes from occurring. This means that they are particularly important for cars that get lower Auto Grades. They’ll help to protect you by keeping you out of crashes in the first place. (Although it’s worth noting that FCW and AEB systems may not protect you from the actions of other drivers).

Driving Deeper

You can learn more about your options by visiting several sites. When performing comparison of Auto Grades, we list FCW as standard or optional technology. If the car that you love gets an Auto Grade that you don’t like, then one possible improvement is to opt for more driver assist technologies like FCW and AEB.

Other good sources of information include:

• The National Highway Transportation Safety Administration lists the standard or optional technologies with the star safety ratings.
• My Car Does What (a site sponsored by the National Safety Council with the University of Iowa) gives nice descriptions of the technologies, along with alternative names.
• Insurance Institute for Highway Safety (IIHS ) has a convenient look-up site for cars.
• Consumer Reports, a membership organization, also has a convenient lookup site for cars.

Glossary

• AEB – Automatic Emergency Braking, a driver assistance system
• CIB – Crash Imminent Braking, a type of AEB system
• DBS – Dynamic Brake Support, a type of AEB system
• FCW – Forward Collision Warning, a driver assistance system
• IIHS – Insurance Institute for Highway Safety
• NHTSA – National Highway Traffic Safety Administration