IIHS: Autobrake Preventing Many Large Truck Crashes

by Gwen Newell

Study shows front crash prevention works for large trucks too

A new study from the Insurance Institute for Highway Safety suggests that equipping large trucks with forward collision warning and automatic emergency braking (AEB) systems could eliminate more than 2 out of 5 crashes in which a large truck rear-ends another vehicle.

Eric Teoh, IIHS Director of Statistical Services, examined data on crashes per vehicle mile traveled from 62 carriers operating tractor-trailers and other trucks weighing at least 33,000 pounds. He found that trucks equipped with forward collision warning had 22 percent fewer crashes and trucks with AEB had 12 percent fewer crashes than those without either technology. Forward collision warning and AEB reduced rear-end crashes – the specific type of collision they’re designed to prevent – by 44 and 41 percent, respectively.

Although their drivers crash less often per mile traveled, large trucks can be especially deadly because they can weigh 20 to 30 times as much as passenger vehicles. U.S. crashes involving large trucks have risen by nearly a third since hitting an all-time low in 2009, killing 4,136 people in 2018. Among those fatalities, 119 deaths resulted from large trucks rear-ending passenger vehicles.

Overall, Teoh’s study covered some 2,000 crashes that occurred over more than 2 billion vehicle miles traveled during 2017 to 2019. The analysis excluded incidents that were not serious enough to result in injury or significant property damage.

Front crash prevention systems use cameras, radar or other sensors to monitor the roadway ahead. Some include only forward collision warning, which alerts the driver to obstacles in the roadway. AEB systems go further – automatically applying the brakes to prevent the collision or reduce its severity.

In the U.S., neither truck nor passenger-vehicle manufacturers are required to equip vehicles with any kind of front crash prevention. However, 20 automakers that account for 99 percent of the U.S. market are moving toward making AEB standard on virtually all new passenger vehicles by September 1, 2022, under a voluntary commitment brokered by IIHS and the National Highway Traffic Safety Administration.

For passenger vehicles, studies conducted by IIHS and the Highway Loss Data Institute have documented significant benefits from AEB. An IIHS study of police-reported crashes showed that from AEB cuts rear-end crash rates in half and rear-end crashes involving injuries by 56 percent. Meanwhile, HLDI has found that AEB cuts property damage liability claims, as well as claims for injuries to people in other vehicles.

The number of large trucks equipped with AEB has been increasing, but there have been few studies of its effect on crash rates. For the new study, Teoh compared trucks from the same carriers that were equipped with forward collision warning alone, AEB, and no front crash prevention at all. AEB systems generally include forward collision warning too.

The similar benefits of forward collision warning and AEB that Teoh observed for rear-end crashes were unexpected, since studies of passenger vehicles have shown AEB to be much more effective than systems that only issue warnings. That could reflect differences in how and by whom trucks and passenger vehicles are driven, or it might be connected to variations among the specific systems used by each carrier.

The study concluded that AEB and forward collision warning are both likely to have benefits beyond the reduction in crashes. Some crashes that are not prevented by the systems are made less severe, thanks to a reduction in impact speed. This is true whether it is the automated system applying the brakes or a human driver who has more time to react because of a warning.

In reviewing the trucks that rear-ended other vehicles, Teoh found that either system resulted in speed reductions of more than 50 percent between the warning or automatic braking and the impact.

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