Rear-end collisions are probably the most common type of collision. Even the most rigorous “statistics-gathering” jurisdictions concede that the actual rate is likely much higher than recorded. This is because many rear-end collisions result in relatively minor injury and damage. The numbers also seem to confound law enforcement. Following another vehicle too closely and driving without due care—the two main causes of rear-enders—support “quasi-criminal” sanction regardless of outcome severity, but the driver of the striking vehicle is rarely ticketed these days.
The main issue becomes liability under the law of negligence applied in civil proceedings. Some rear-end collisions result in enormous damage and sometimes kill people. The problem is huge, and over a hundred years of experience has proved that there are no easy answers.
When “a platoon of many consecutive tailgaters forms” (as Leonard Evans puts it in the book “Traffic Safety”) reactions to decelerating vehicles in front need to be increasingly prompt. If the platoon is long enough and the deceleration rate high enough, eventually a multi-vehicle pile-up—with a potentially horrific outcome—“becomes inevitable.”
Maintaining a speed-safe following distance is a constant driving challenge. In dense traffic, the inevitable gap is always being filled in. In moderate traffic, where vehicles can maintain a constant speed and distance, the static visual impression tends to lower awareness and concern. And, as Dr. Evans puts it, “experience, that false educator, has taught [us] that [we are] is safe.”
In the last couple of years, some automobile manufactures have started to explore technology options designed to help avoid rear-end collisons altogether. The technology will compensate for “human factors” that are inadequate. Sudden perception of danger tends to interfere with our judgment and reaction time. The average driver takes about 1.1 seconds to react before braking, a loss of precious time. Research by one automaker indicates that in half of all rear-end collisions, the brakes are never even applied by the oncoming driver.
Even a slight reduction in speed before a crash can avoid a fatal result. Accordingly these systems—called by various names—detect obstacles by lasers or sensors or cameras, warn the driver by visual or aural signals or both, activate the braking system, tighten the seatbelts and engage the airbags. If the driver’s braking is measurably insufficient, the system engages independently. In effect, as one commentator describes it, “while the driver [is] frozen in terror, the car [is] navigating out of an accident.” This past year, one European developer has launched a “closing velocity detector” system that makes such functionality affordable for small and mid-range vehicles.
Dr. Evans’ response to “take control from the driver” technology is less than enthusiastic, however. He writes, “Even if the technology were perfect, the risk would be high. If our vehicle were unable to match the braking of the lead vehicle, we would hit it. …We would be especially vulnerable if a slippery patch of roadway surface was encountered at the wrong time.”
However, we can expect “closing velocity detectors” on vehicles in the near future, not so much for the purpose of taking control in a crisis, but simply to warn of an upcoming danger.