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Status Report, Vol. 48, No. 10 | December 30, 2013 Subscribe

Softer vehicle fronts and pedestrian detection systems could reduce pedestrian deaths, injuries

IIHS engineers are evaluating the performance of pedestrian detection systems on the test track at the Vehicle Research Center.

Improved crashworthiness and growing availability of systems to help drivers avoid crashes have made roads safer for vehicle occupants. Now engineers are working on improvements to vehicles that could protect pedestrians, too.

A new Institute analysis finds that a proposed regulation to modify the front of vehicles to lessen the harm they cause to pedestrians in crashes can help reduce deaths and injuries. The finding is important because few studies have examined the real-world effects of these vehicle design changes. At the same time, the Institute has been studying how pedestrian detection systems, which alert a driver to a person in the vehicle's path and in some cases brake automatically, perform on the test track.

Because deaths in all other types of passenger vehicle crashes have fallen dramatically during the past decade, pedestrian fatalities make up an increasing percentage of crash deaths. In 2012, 4,743 pedestrians were killed in the U.S., accounting for 14 percent of crash deaths. In contrast, the 4,851 pedestrians killed in 2002 made up 11 percent of crash deaths. The vast majority of pedestrian crashes involve a single passenger vehicle, and most of these are frontal crashes (see "Pedestrians stand to benefit from new vehicle technology and design changes," March 30, 2011). The most common scenario involves a person crossing a roadway and a vehicle traveling straight. When pedestrians are seriously injured, the head is the most commonly injured body region.

One approach to the problem of pedestrian deaths and injuries is to modify the fronts of vehicles to make them "softer" if they contact a pedestrian. The idea stems from research dating to the 1970s, but its real-world application has taken hold only recently.

Crushable hoods and fenders cushion heads, and padding in bumper systems can mitigate leg injuries. Using plastic hood mounts and headlights that break away on impact also are intended to reduce chances that pedestrians will be injured.

Pedestrian airbags are another strategy. The Volvo V40 hatchback sold in Europe is the first vehicle equipped with an external airbag to protect a pedestrian's head in a crash. If sensors detect an imminent collision, the airbag deploys from beneath the car's upper hood to cover a portion of the windshield and windshield pillars.

Volvo and other automakers in the European market have made such design changes to comply with European Union rules on protecting pedestrians in crashes. Under a two-tier regulation that took effect in 2004, all passenger vehicles must pass crash tests that assess the risk of injury to an adult's head, a child's head and an adult's knee and lower leg. By 2018, 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. In the future, vehicles with pedestrian detection may be exempt from second-tier tests.

Volvo recently signaled it might shelve plans to broaden adoption of pedestrian airbags beyond the V40, choosing instead to focus on its pedestrian detection system, which the manufacturer views as more promising, media reports indicate.

In the U.S., the National Highway Traffic Safety Administration (NHTSA) has been considering a global technical regulation since 2009 that would require tests to address pedestrian head-to-hood impacts for adults and children. The regulation known as GTR 9 is part of a United Nations' effort to harmonize certain vehicle safety standards worldwide. GTR 9 would require head impact tests for vehicle hoods but not the windshield and windshield pillar tests European regulators mandate. GTR 9 also addresses pedestrian leg-to-bumper impacts.

A 2012 IIHS study compared patterns of injuries sustained by pedestrians treated at a Washington, D.C.-area trauma center with the parts of the vehicle that would be affected by GTR 9 tests. Researchers found that the proposed regulation would address some but not all of the injuries seen in these real-world crashes.

In the latest IIHS pedestrian study, the goal was to compare the broader European tests and the narrower GTR 9 tests in terms of potential reductions in head injuries in U.S. crashes. Researchers conducted a series of head-impact tests on seven 2002-07 model small cars. They compared the predicted risk of injury from these tests to the real-world pedestrian injury and fatality rates for the same models based on data from police-reported pedestrian crashes in 14 states. None of the vehicles in the study were designed specifically for regulatory tests for pedestrian protection, although some models were associated with fewer serious injuries.

Researchers found that both the European and GTR 9 tests were good predictors of pedestrian injuries and fatalities. Europe's regulations showed a slightly bigger benefit because the crash tests address more of the relevant portions of the vehicle typically struck by pedestrians' heads. No matter the test zone, however, softer vehicle components were associated with a lower risk of fatal injury.

"Both the European and proposed U.S. regulations look to be beneficial," says David Zuby, the Institute's executive vice president. "They are a step in the right direction until pedestrian detection systems become commonplace in U.S. vehicles."

Crash avoidance technology to prevent or mitigate crashes with pedestrians is an approach that holds promise. Radar or camera-based systems are designed to spot pedestrians entering a vehicle's path and either warn the driver or automatically brake if the driver fails to react. Subaru's EyeSight and Volvo's Pedestrian Detection with Full Auto Brake are two examples (see "Cars can brake for pedestrians if drivers don't," March 30, 2011).

"Systems like these are still relatively new to the U.S. market and aren't available on many vehicles in the current fleet," says Zuby. "At our Vehicle Research Center, we're studying how pedestrian detection systems perform in test track evaluations. Our goal is to develop a ratings system to help consumers compare features by vehicle, similar to the front crash prevention ratings we launched in 2013."

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