Study finds that Forward Collision Warning (FCW) and automatic emergency braking (AEB) were associated with 44 percent and 41 percent reductions, respectively, in the rear-end crash rate of large trucks.
The Insurance Institute for Highway Safety (IIHS) study used data on crashes during 2017-19 of Class 8 trucks (mostly tractor-semitrailers with a gross vehicle weight rating of 33,000+ pounds) from SmartDrive Systems.
Made Public Date


United States

Effectiveness of front crash prevention systems in reducing large truck crash rates

Summary Information

Front crash prevention systems, namely forward collision warning (FCW) and automatic emergency braking (AEB), monitor the road environment ahead using radar and/or video camera sensors. FCW systems typically sound an audible alert if a front collision is likely, allowing the driver to begin an avoidance maneuver. AEB systems, which generally include FCW functionality, apply the vehicle’s foundation brakes to prevent or mitigate a forward impact if the driver does not intervene.

Some FCW systems have the advantage of being able to be retrofitted to existing trucks, so benefits can be realized sooner and with less investment. AEB systems are more common in the passenger vehicle fleet. Although no federal mandate exists for AEB, 20 automakers representing 99 percent of the United States automobile market have agreed to make AEB standard on virtually all new passenger vehicles by September 1, 2022.

While FCW and AEB systems have been shown to reduce front-to-rear crash rates for passenger vehicles, less is known about their effectiveness in large trucks. Therefore, this study sought to better understand their effectiveness as countermeasures for crashes with large trucks.


Data on Class 8 trucks operating on limited-access highways during 2017–2019 were obtained from SmartDrive Systems. All 62 carriers in the study operated trucks both with and without front crash prevention technologies, and many operated trucks with only one of the front crash prevention systems. Detailed data on exposure measures and crash circumstances were extracted from video footage by both automated means and manual coding. Crash rates were compared by front crash prevention technology (FCW, AEB, neither) for all police-reportable crashes and for relevant crash types. 



FCW was associated with a statistically significant 22 percent reduction in the rate of all police-reportable crashes per vehicle miles traveled of large trucks, and a significant 44 percent reduction in the rate of rear-end crashes. AEB was also associated with significant reductions—12 percent overall and 41 percent for rear-end crashes. On average, speed was reduced by over half between the time of the intervention and impact for both systems. 

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