By Dr. Ensar Becic
In August, we concluded an investigation of a fatal rear-end crash that occurred in Cranbury, New Jersey, in which the striking vehicle (truck-tractor combination vehicle) was equipped with an older model collision warning system (CWS). This system did not prevent the crash, and our investigation found no evidence that the system alerted the driver of the impending collision.
Even if the warning had alerted, it would not have come in time to prevent the crash. The good news is that current generation forward collision avoidance systems (CAS ) — a CWS is just one type of CAS technology — detect crashes sooner and with more accuracy.
In May, we released a report recommending passenger and commercial vehicle manufacturers install collision warning and autonomous emergency braking systems as standard equipment in all new vehicles. The report also urged the National Highway Transportation Safety Administration to expand or develop protocols for the assessment of forward collision avoidance systems in passenger and commercial vehicles.
Why is continued evaluation of technologies important? So that we don’t have crashes like the one we saw in Cranbury.
Whether a crash is prevented — or the extent to which it is mitigated — depends on the speed of the vehicles involved and the quality of the CAS in use. These issues must be considered when developing and evaluating the effectiveness of forward CAS in all vehicle types.
Let’s take a closer look at the Cranbury crash. The truck-tractor was traveling at 65 mph when approaching a line of nearly stopped vehicles — an extreme rear-end crash scenario. The truck-tractor was equipped with a CWS, which was designed to warn a driver about 2.5–3 seconds prior to a collision. Our accident reconstruction revealed that the driver of the truck-tractor steered 1.5–2 seconds before impacting the vehicle ahead, an avoidance maneuver. Although the maneuver came very late, it likely mitigated the severity of the crash.
The truck driver involved in the crash was extremely fatigued, and we found no evidence that a warning was presented. A fully alert driver would have noticed the slowed traffic well before the onset of a warning; however, drivers aren’t always fully alert.
Would a properly functioning CWS effectively warn even a rested driver in time to avoid the crash completely? Sadly, in the Cranbury accident, not much would have changed.
While it is possible that the truck driver did receive a warning — which prompted him to steer at the very last moment — it is also clear that the 3-second warning would not have been sufficient to prevent this extreme crash. Even if this truck had been equipped with the new generation of these systems, many of which have a longer warning time, it still would have been difficult to completely prevent this crash. But the damage caused by the crash might have been further mitigated.
Preventing crashes involving vehicles traveling at high speeds is very challenging. But even mitigation of such crashes can make a difference between a fatality and an injury.
Developing forward collision avoidance systems that can prevent all rear-end crashes is a lofty goal, but through continuous technological advancements and research, and more demanding regulatory standards, it is possible.
The NTSB has recommended to the National Highway Traffic Safety Administration that it achieve this goal. In the meantime, we can reap the incremental benefits along the way: fewer crashes, fewer deaths, and less severe injuries.
We should never give up on pursuing technologies that save lives.
Ensar Becic, Ph.D., is a project manager and human performance investigator in the NTSB Office of Highway Safety.