Most front crash prevention systems include forward collision warning and automatic emergency braking (AEB). Forward collision warning alerts the driver when a rear-end crash is imminent, and AEB automatically slams on the brakes if the driver fails to respond in time.
Today’s systems reduce rear-end crash rates with medium or heavy trucks by 38 percent and rear-end crash rates with motorcycles by 41 percent, compared with a 53 percent reduction in rear-end crash rates with other passenger vehicles, an IIHS study of more than 160,000 crashes found. The same discrepancy is seen with the surrogate vehicle targets that IIHS and other organizations use to evaluate system performance, another study demonstrated.
“These reductions are impressive for all vehicle types, but the safety benefits could be even larger if front crash prevention systems were as good at mitigating and preventing crashes with big trucks and motorcycles as they are with cars,” said Jessica Cicchino, IIHS vice president of research.
Specifically, such systems could prevent an additional 5,500 crashes a year with medium or heavy trucks and another 500 crashes with motorcycles.
The effect on fatalities could be substantial too. A medium or heavy truck or a motorcycle is struck by a passenger vehicle in about 43 percent of fatal rear-end crashes, even though another passenger vehicle is the struck vehicle in 97 percent of rear-end crashes overall, an earlier IIHS study showed.
“Motorcycles and large trucks present unique risks,” Cicchino said. “Along with being hard for other drivers to see, motorcycles don’t have a steel frame surrounding and protecting the rider the way cars do. At the other end of the spectrum, large trucks are so massive that when a passenger vehicle hits one, it’s more likely to be fatal to the people inside the passenger vehicle. The height of large trucks can also result in dangerous underride crashes.”
To determine how well today’s front crash prevention systems are addressing these crashes in the real world, Cicchino and IIHS Senior Research Scientist David Kidd compared police-reported rear-end crash rates for model year 2016-20 passenger vehicles with and without AEB and forward collision warning when the struck vehicle was another passenger vehicle, a medium or heavy truck or a motorcycle. The crash data used were police-reported crashes during 2017-21 in 18 U.S. states.
The researchers found that front crash prevention was associated with a 53 percent reduction in rear-end crashes involving another passenger vehicle, a 38 percent reduction in rear-end crashes with medium or heavy trucks and a 41 percent reduction in rear-end crashes with motorcycles.
When IIHS first began evaluating front crash prevention systems 10 years ago, few vehicles were equipped with forward collision warning or AEB, and even fewer systems qualified for an advanced or superior rating. Today practically every new passenger vehicle has the feature thanks to a voluntary manufacturer commitment brokered by IIHS and the National Highway Traffic Safety Administration. For several years running, virtually every vehicle tested has earned the Institute’s highest rating of superior in the vehicle-to-vehicle evaluation.
No longer part of the criteria for the Institute’s TOP SAFETY PICK and TOP SAFETY PICK+ awards, that earlier test was conducted at 12 mph and 25 mph with a target representing a passenger car.
To make sure systems are equally adept at preventing crashes with large trucks and motorcycles and to address the large portion of rear-end crashes that happen at higher speeds, IIHS is conducting a new vehicle-to-vehicle front crash prevention evaluation, with plans to publish the first updated ratings early next year.
As part of that process, Kidd partnered with researchers from Transport Canada to gauge how various front crash prevention systems react to different vehicles and surrogate targets. In total, the two organizations examined how five 2021-22 models from Acura, Subaru, Toyota, Volkswagen and Volvo reacted to 12 different nonpassenger vehicles or surrogate targets and seven different passenger vehicles or surrogate targets. Anticipating the higher speeds of the future IIHS program, the researchers conducted the tests at 31 mph, 37 mph and 44 mph.
“We’re pleased to be participating in this unique collaboration with IIHS, a leader in vehicle safety testing,” said Dr. Peter Burns, head of vehicle crash avoidance and human factors research at Transport Canada. “Transport Canada is committed to advancing road and vehicle safety in Canada and worldwide.”
In general, the study showed that front crash prevention systems aren’t as good at detecting other types of vehicles and surrogate targets as they are at detecting a standard passenger car target.
All five test vehicles earn the highest rating of superior in the original IIHS vehicle-to-vehicle front crash prevention evaluation. However, Kidd and his co-authors found that the systems were substantially less likely to sound an alert when a collision with certain large vehicles or with a motorcycle target was imminent than when the test vehicles were approaching the standard passenger car surrogate.
“Motorcycles are smaller and narrower than cars, making them more difficult for camera- and radar-based systems to identify, especially at higher speeds,” Kidd said. “Extra-large vehicles are presumably easier to detect, but their dimensions appear to confuse the systems’ algorithms.”
When approaching the standard passenger car target, the test vehicles sounded forward collision warning alerts in about 9 out of 10 trials. Results were statistically equivalent for most of the other target vehicles and surrogates, which included two other passenger car surrogates and a BMW X5 SUV, Ford F-250 pickup and Nissan Altima sedan among other vehicles. In contrast, the test vehicles warned of impending collisions with a school bus, fire truck, tractor trailer and dry van trailer in fewer than 8 out of 10 trials and in only about 7 out of 10 trials with the two motorcycle targets.
“This research shows that front crash prevention testing programs need to use a variety of targets representing different vehicle types to ensure good performance in the real world,” Kidd said. “Our updated test will make use of the two standard motorcycle targets as well as a new passenger car target, and we’ll evaluate warning responses to a real tractor-trailer.”