Ok, I think you miss the point (and there's more research than is summarized in TFA)...when roads feel safe, drivers are more careless and so traffic accidents per passenger mile go up. When roads feel more dangerous, drivers are more careful and traffic accidents per passenger mile go down. This is the same reason all the tech in cars has not saved as many lives as projected...drivers compensate for the added safety of anti-lock brakes by driving more aggressively.