More Information Worth Knowing about Forward Collision Warning & Automatic Emergency Braking

 In Car Safety Rating Systems, Vehicle Safety

Sorting out new crash avoidance and driver assistance technologies like automatic braking system can be very difficult. In 4 Questions to Ask When Buying a Car with Forward Collision Warning & Automatic Emergency Braking, you find an introduction to get started learning about these systems. You can also find some important questions to ask your salesman when thinking about purchasing this technology.

In this post, we dig deeper into how Forward Collision Warning (FCW) and its companion technology Automatic Emergency Braking (AEB) are typically designed to operate.

A Voluntary Commitment

How did automatic braking system become a common safety feature? The National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) work with 20 automotive manufacturers. The manufacturers represent 99% of the U.S. car market and put in place a voluntary government-industry commitment.  They signed the commitment in 2016. The automakers agreed to make an Automatic Emergency Braking (AEB) system a standard feature on nearly all new vehicles by model year 2022. The agreed-upon AEB system must have two features, Forward Collision Warning and Crash Imminent Braking (CIB).

This sounds confusing and not very helpful for a car buying decision today. So, we use the system requirements defined in the agreement as an example of how FCW and CIB are designed to work.

Passing the Test(s)

When manufacturers design FCW and AEB systems, they decide on when and how the systems will work. Per the voluntary agreement, a FCW system is required to pass two tests developed by NHTSA:

Test #1

Test #2

The CIB system requires meeting one of two options, using procedures developed by the IIHS, to honor the commitment:

  • The CIB-equipped vehicle must achieve average speed reduction greater than 10 mph when approaching a stopped vehicle while traveling at either 12 or 24 mph.


  • The CIB-equipped vehicle must achieve average speed reduction greater than 5 mph when approaching a stopped vehicle while traveling at both 12 and 24 mph.

Limitations of FCW and CIB to Consider

None of these tests require FCW or CIB to function in high speed environments, e.g., when traveling at 55 mph.

Also, there are other limitations on these situations that may surprise you. They are listed in the NHTSA and IIHS test procedure documents and specifically say that neither the FCW nor CIB systems are tested in conditions of inclement weather.  “Inclement weather” includes (but isn’t limited to) rain, snow, hail, fog, smoke, and ash.  The disclaimer means that the FCW and CIB systems may not function in those situations.  The limitation is particularly unfortunate, since those are the kind of conditions that make driving more dangerous. As always, additional driver support would be welcomed.

Neither FCW nor CIB systems are tested in conditions of inclement weather, including but not limited to rain, snow, hail, fog, smoke and ash.

When you consider purchasing a car with these features, it may be useful to check if these systems will be helpful to you as you navigate the weather in your particular geographical region.


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, no matter the weather or the speed.

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 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).

So, if the car that you love gets an Auto Grade you don’t like, one possible improvement is to opt for more crash avoidance technologies like FCW and AEB.

Working together to create a world where everyone walks away from a crash.