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Status Report, Vol. 46, No. 3 | March 30, 2011 Subscribe

Pedestrians stand to benefit from new vehicle technology and designs

Big strides in crash protection have been made for people riding in passenger vehicles, but the same can't be said for pedestrians. People, after all, don't come with airbags. Now engineers are trying to make vehicles safer for people outside them, too, by adding technology to help drivers avoid hitting pedestrians and design features to soften impacts.

Technology has the potential to avert many of these crashes altogether. Automakers are developing systems to spot pedestrians entering a vehicle's path and to automatically brake if the driver fails to react. One such system already is on the U.S. market (see sidebar), and more are in the works. A new Institute study on pedestrian crashes shows what kind of situations such technology should be equipped to handle. Researchers found the most common scenario involves a person crossing a roadway and a vehicle traveling straight. In most cases, nothing blocks the driver's view of the pedestrian, and no braking is reported. Such crashes usually happen during the day, although most of the fatal ones occur at night.

"The best way to protect pedestrians is to separate them as much as possible from vehicle traffic," says David Zuby, the Institute's chief research officer. "But the paths of walkers and drivers inevitably are going to intersect at some point, and new warning systems, as well as vehicle design changes required in Europe, have the potential to make those meetings less deadly."

Overall highway deaths have fallen to their lowest levels since 1950, and much of the decline in recent years is due to safer vehicles. Pedestrian fatalities have fallen, too, but that may simply be a result of people walking less. Still the death toll remains high: In 2009, 4,092 pedestrians were killed, accounting for 12 percent of all crash fatalities in the United States.

Tried and true methods for reducing pedestrian crashes generally involve roadway design changes. Pedestrians and vehicles can be separated with sidewalks, overpasses, and refuge islands in the middle of busy two-way streets. Better lighting and pedestrian countdown signals can help, as can reducing vehicle speeds and banning right turns on red. But such solutions haven't always been implemented consistently and can't address every risky scenario, which is why technology could play a key role.

Crash avoidance technology

Systems aimed at preventing or lessening the severity of pedestrian crashes are an offshoot of a more common type of crash avoidance feature known as forward collision warning. Such systems alert the driver if the vehicle is about to crash with a vehicle ahead of it and, in some cases, apply the brakes automatically if the driver fails to respond. A pedestrian detection system is a forward collision warning system that has been enhanced to recognize not just vehicles, but people too.

Forward collision warning is offered on 19 vehicle makes in 2011 and is one of several crash avoidance features that have been gaining ground. (Others are lane departure warning, side view assist, and adaptive headlights.) The Institute has estimated that as many as 1.2 million crashes, including 879 fatal crashes, could be prevented or mitigated each year if all vehicles were equipped with forward collision warning (see "New estimates of benefits of crash avoidance features on passenger vehicles," May 20, 2010). Pedestrian detection systems could prevent an additional 39,000 crashes, including 2,932 fatal ones, researchers estimate.

As automakers continue to work on this technology, the Institute conducted its latest study to help guide their designs. Looking at federal crash data from 2005-09, researchers found the vast majority of pedestrian crashes involved a single passenger vehicle, and most of those were frontal crashes. Ninety-five percent of people struck by the front of a vehicle and more than three-quarters of those who died were crossing traffic as opposed to walking along the road.

Eight of 10 pedestrians who were killed while crossing traffic, as well as a majority of those who were struck but didn't die, were hit by drivers who were going straight with no visual obstruction. That scenario accounted for a majority of all frontal collisions between passenger vehicles and pedestrians and 61 percent of the fatalities.

Other kinds of crashes were far less common. The second most common one, involving a turning vehicle with no visual obstruction and a person crossing the road, accounted for about a quarter of pedestrians struck by the front of a vehicle and 4 percent of those who died. The second most common type of fatal crash, involving a vehicle going straight with no view obstruction and hitting a person walking in line with traffic, was responsible for 12 percent of pedestrian deaths.

So-called dart-outs, in which a person appears suddenly in the roadway from behind a parked vehicle or other obstruction, were even less common.

Of the cases involving vehicles going straight without view obstruction, drivers hit the brakes in only 13 percent of both fatal and nonfatal impacts. In other words, most drivers who hit pedestrians crossing the roadway apparently never react to what's in front of them. That means pedestrian detection systems have a lot of potential to avert crashes by acting as an extra set of eyes and an extra foot above the brake pedal.

Frontal crashes with single passenger vehicles, 2005-09

graphic

Of course, a system that recognizes an impending collision only after the pedestrian is directly in front of the vehicle would hold limited value. The trick is developing technology that can accurately predict when someone is going to step into the path of a vehicle.

"Pedestrians can change course quickly, so just as it can be hard for a driver to know what a person at the curb is going to do, it also can be tricky for a computer," Zuby says. "It's important to get that right because too many false alarms could turn a warning system into an annoyance and make drivers reluctant to accept the new technology."

Another finding relevant to developers of pedestrian detection systems is that three-quarters of people struck were on roads with speed limits of less than 40 mph. Fatalities, however, were more evenly distributed. Roads with speed limits of 30-39 mph, 40-49 mph, and over 49 mph each accounted for more than a quarter of them.

The biggest hurdle for the new technology is how to prevent crashes that occur at night. The systems on the market now rely on light-dependent cameras. Most frontal collisions with pedestrians occur during the day, so these systems could be expected to take a bite out of the overall pedestrian crash problem. But with more than two-thirds of fatalities occurring after dark, significantly cutting pedestrian deaths will require technology that can perform reliably with limited or no light.

Europe's approach

Crash avoidance technology is just one aspect of the effort to improve passenger vehicles to protect pedestrians. Another strategy is to modify the fronts of vehicles to lessen the harm they can cause to a person who is struck. New regulations in the European Union are taking this route.

As of September 2010, all passenger vehicles must pass crash tests that assess the risk of injury to an adult's head, a child's head, and adult's knee and lower leg. By September 2015, automakers must comply with a second phase that has stricter standards for the head and leg and also tests the impact that the hood's edge would have on a person's hip.

To meet the new requirements, automakers are putting more room between the hood and engine, designing hoods that automatically raise up a few inches from the engine upon impact, installing hood airbags, hiding hard elements like windshield wipers, and designing softer bumpers for their vehicles sold in Europe. It's too soon to tell whether these changes are reducing pedestrian injuries.

In the United States, the National Highway Traffic Safety Administration conducted research from the 1970s through the early 1990s that could have led to similar requirements, but that effort was scuttled (see Status Report special issue: pedestrian injuries, March 13, 1999). The agency never made clear its reasons for abandoning the idea, but the motivation for it likely faded as pedestrian fatalities continued to drop on their own.

Nevertheless, some version of the European tests may come to the U.S. in the future as part of an effort to standardize such regulations across the globe.

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