An NHTSA report [PDF] on the “Incidence of Pedestrian and Bicyclist Crashes by Hybrid Electric Passenger Vehicles,” concludes that hybrid-electrics (HEVs) have a higher incidence rate of pedestrian and bicyclist crashes than do internal combustion-only (ICE) vehicles in certain scenarios. And based on the report’s conclusions, it looks like the relative silence of hybrids running in electric-only mode is to blame for the higher accident numbers.
. . . pedestrian and bicyclist crashes involving both HEVs and ICE vehicles commonly occurred on roadways, in zones with low speed limits, during daytime and in clear weather, with higher incidence rates for HEVs when compared to ICE vehicles. A variety of crash factors were examined to determine the relative incidence rates of HEVs versus ICE vehicles in a range of crash scenarios. For one group of scenarios, those in which a vehicle is slowing or stopping, backing up, or entering or leaving a parking space, a statistically significant effect was found due to engine type. The HEV was two times more likely to be involved in a pedestrian crash in these situations than was an ICE vehicle. Vehicle maneuvers such as slowing or stopping, backing up, or entering or leaving a parking space, were grouped in one category based on that these maneuvers are potentially have occurred at very low speeds where the difference between the sound levels produced by the hybrid versus ICE vehicle is the greatest.
At speeds above 35 MPH, the statistical differences between the percentage of hybrids and ICE vehicles involved in pedestrian and cyclist crashes are insignificant. Below those speeds, and while engaging in the maneuvers described above, the statistical difference becomes clear. What this indicates is that the silence of electric drive vehicles is, statistically speaking, a safety issue. Expect this study to figure into ongoing efforts to pass legislation, like H.R. 734, requiring sound standards for electric-drive vehicles.