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Status Report, Vol. 44, No. 11 | December 22, 2009 Subscribe

Hybrids may prompt pedestrians, cyclists to prick up their ears

Most grade-schoolers learn to stop, look, and listen before they cross the street. Now the listening part may be getting harder for people of all ages as quiet-engine hybrid vehicles proliferate. A new federal study reports that hybrid electric cars are more likely than models with internal combustion engines to crash with pedestrians and bicyclists, especially during low-speed maneuvers when the hybrids are likely to be running only on electricity.

Conducted by Refaat Hanna for the National Highway Traffic Safety Administration, the study relies on police reports of collisions in 12 states to compute proportions of crashes involving pedestrians and bicyclists colliding with Honda and Toyota hybrids versus similar cars from the same automakers without hybrid engines. In comparing crash rates for the vehicle groups, Hanna noted their wind and tire noise. The hybrids' overall likelihood of crashing with a pedestrian was 40 percent higher than that of the other cars, increasing to a 50 percent difference in areas where speed limits were 35 mph or slower.

Hanna looked specifically at crashes that occurred when cars were slowing or stopping, backing up, or entering or leaving a parking space because such maneuvers usually occur at very low speeds — important because hybrids operate mostly on electric power at such speeds, so this is when the sound difference is greatest compared with other cars. The percentage of hybrid crashes involving pedestrians in these situations was twice as high as it was for nonhybrids. There was no significant difference between the crash rates of the 2 groups of cars when they were traveling straight down a road.

Rates of bicyclist crashes, like those involving pedestrians, were higher for the hybrids than for the other group of cars. Again, the differences were greatest among crashes that involved maneuvers at very low speeds.

This study isn't based on large numbers, and Hanna concedes that "a larger sample would allow us to perform a more detailed analysis." He adds that the study is too limited to estimate the size of the quiet-engine hazard nationwide.

"Hanna reports some useful findings about an issue that first was raised by the National Federation of the Blind and others," Anne McCartt, Institute senior vice president for research, points out. "The differences in crash rates are substantial enough that we believe quiet vehicles may be a concern for all pedestrians and bicyclists, not just those who are blind."

This concern is likely to grow as hybrid cars proliferate. Back in the 2000 model year there was a single hybrid model, the Honda Insight. In contrast, the total is 33 hybrids among 2010 models. Registrations of new hybrids increased 38 percent between 2006 and 2007 alone.

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