Front Crash Prevention Works, Says IIHS
“The success of front crash prevention represents a big step toward safer roads,” said David Zuby, IIHS chief research officer. “As this technology becomes more widespread, we can expect to see noticeably fewer rear-end crashes. The same goes for the whiplash injuries that often result from these crashes and can cause a lot of pain and lost productivity.”
In September, the National Highway Traffic Safety Administration (NHTSA) and IIHS announced an agreement in principle with automakers to make autobrake standard on all new-car models.
The IIHS study looked at police-reported rear-end crashes in 22 states during 2010-14 involving Acura, Honda, Mercedes-Benz, Subaru, and Volvo vehicles with optional front crash prevention. Researchers compared the crash rates of vehicles equipped with that technology with the crash rates of the same models without it. The researchers identified individual vehicles with the technology using trim level information or, in some cases, lists of vehicle identification numbers supplied by the manufacturers.
IIHS researchers also conducted a separate analysis of City Safety, Volvo's standard low-speed autobrake system, comparing the Volvo S60 with other midsize luxury 4-door cars and the Volvo XC60 with other midsize luxury SUVs. None of the comparison vehicles had standard front crash prevention.
The researchers only considered rear-end crashes in which the study and comparison models struck other vehicles. Crashes in which those vehicles were struck from behind but didn't strike a vehicle in front were left out, since front crash prevention wouldn't be expected to prevent them. Control factors included information on the vehicle’s garaging location and driver characteristics.
The analyses show that forward-collision warning alone reduced rear-end crashes by 23%, while forward-collision warning with autobrake reduced them by 39%. Volvo’s City Safety reduced rear-end crashes by 41%. The rate of rear-end crashes with injuries decreased by 42% with forward-collision warning with autobrake, and by 47% with City Safety.
City Safety had the biggest effect on roads with speed limits of 40 to 45 mph. The equipped Volvos rear-ended other vehicles 54% less frequently than comparable vehicles on those roads. The reduction was 39% on roads with speed limits of 35 mph or less, and 25% on roads with speed limits of 50 mph or higher. The IIHS attributes this disparity to the fact that roads with speed limits of 40 or 45 mph tend to have many traffic lights, which reduce actual travel speeds. Moreover, City Safety can come into play when traffic is congested on a higher-speed road.