In the United States, the animal most likely to cause a traffic accident is the opossum. There are two reasons for this (in addition to its relative abundance compared to other animals). 1) Some people find it so cute when it waddles across the road that they frantically swerve to avoid it, and 2) some people, having never seen an opossum before, think it's a giant rat and swerve frantically to try and hit it.