Front crash prevention systems are designed to intervene when the vehicle is about to rear-end another vehicle. The technology uses various types of sensors, such as cameras, radar or lidar — short for light detection and ranging — to detect when the vehicle is getting too close to one in front of it. The systems generally issue a warning and precharge the brakes to maximize their effect. Most also apply the brakes if the driver doesn’t respond.
Front crash prevention is becoming more universal and its capabilities more consistent across brands, thanks to a voluntary commitment by 20 automakers, representing 99% of U.S. light vehicle sales, to make the technology standard by September 2022. The commitment, brokered by IIHS and the National Highway Traffic Safety Administration (NHTSA), called for vehicles to have systems with both a forward collision warning component that met NHTSA criteria and automatic braking that achieved certain minimum speed reductions in IIHS track tests.
Many front crash prevention systems can detect pedestrians, and some also recognize cyclists and animals. These systems use advanced algorithms coupled with sensors and cameras to spot nonmotorists who are in or about to enter the vehicle’s path.
Vehicles equipped with front crash prevention are much less likely to rear-end other vehicles than the same models without the technology (Fildes et al., 2015; Isaksson-Hellman & Lindman, 2016; Cicchino, 2017). An Institute study found that systems with forward collision warning and automatic braking cut rear-end crashes in half, while forward collision warning alone reduces them by 27%. The autobrake systems also greatly reduce rear-end crashes involving injury.
A separate IIHS study showed that automatic braking systems that recognize pedestrians cut pedestrian crashes by 27% (Cicchino, 2022).
Passenger vehicles are not the only vehicles that benefit from front crash prevention systems. Similar rear-end crash reduction effects have been found for large trucks equipped with front crash prevention systems (Teoh, 2021).
HLDI has conducted studies comparing insurance claim rates for passenger vehicles equipped with front crash prevention with claim rates for the same models without the technology. Vehicles equipped with these systems consistently show lower rates of claims for damage to other vehicles and for injuries to people in other vehicles (HLDI, 2023).
Similarly, HLDI found that Subaru’s EyeSight system with pedestrian detection cut the rate of likely pedestrian-related insurance claims by 35%, compared with the same vehicles without the system (Wakeman et al., 2019).
Even if a front crash prevention system doesn’t avoid a crash altogether, it may still reduce the impact speed, thereby making a crash less severe.
To show why reducing speed is important, IIHS conducted two demonstration crash tests at different speeds in 2013. In each test, a 2013 Mercedes-Benz C-Class ran into the back of a stationary 2012 Chevrolet Malibu. The tests illustrated what happens in a 25 mph crash when the striking vehicle doesn’t have autobrake, compared with what happens when the speed is reduced by 13 mph, the amount by which the C-Class's autobrake system reduced the impact speed in IIHS track testing. Damage in the higher speed crash test was about $28,000. The Malibu was a complete loss. Lowering the speed to 12 mph trimmed the damage to $5,700 (IIHS, 2013).
A similar speed reduction in a higher-speed crash could significantly reduce injury risk as well as vehicle damage (Kraft et al., 2009).
Front crash prevention systems with automatic braking have resulted in bigger reductions in rear-end crashes with injuries than in rear-end crashes of all severities, which suggests that these systems are preventing injuries in some rear-end crashes that aren’t avoided (Cicchino, 2017).
IIHS has rated front crash prevention systems since 2013 and began rating pedestrian detection systems in 2019.
NHTSA issued a regulation in 2024 that requires all new passenger vehicles to be equipped with automatic braking that can avoid rear-end crashes with other vehicles and crashes with pedestrians by September 2029 (Office of the Federal Register, 2024). Pedestrian detection would be required to work in both daylight and dark conditions.