I am a runner, and recently I have had several close calls on the road with hybrid cars, such as the Toyota Prius. Hybrid cars are quieter, and the quietness of these cars could increase the risk of pedestrian accidents.
This concern was recently noted by David Strickland, the new administrator of the National Highway Traffic Safety Administration. Speaking at the Society of Automotive Engineers World Congress, Strickland said that the NHTSA was conducting research with respect to hybrid vehicles and risks to pedestrian safety. Although there does not appear to be any statistics that confirm an increased number of auto/pedestrian accidents due to hybrid vehicles, the quietness of these vehicles are definitely a concern for pedestrian safety. Quieter vehicles could pose a risk to pedestrians in a cross walk, and also to children who might be less conscious of a vehicle approaching. The NHTSA is reportedly considering measures to address the concern of quiet vehicle contributing to pedestrian accidents, including researching whether a requirement to add a "noise emitting system" to hybrid vehicles is a good idea.
In past years when running on the roads, I had a pretty good sense of where cars were even if I could not see them. With the increased number of hybrid vehicles on the road, extra caution is required to insure that a pedestrian-auto accident is avoided.