With 17.5 million drivers (8.5%) stopped in 2005, traffic stops are the most frequent contact between cops and citizens. People of any race are equally likely to be pulled over by police in a traffic stop. But once on the side of the road, are any groups more of less likely to receive harsh treatment?

A 2005 Justice Department Study, which interviewed 64,000 citizens to collect its data, concluded that Blacks and Hispanics are more likely to be searched (B-9.5%, H-8.8%, W-3.5%), arrested (B-4.5%, H-3.1%, W-2.1%), and threatened with or subjected to force (B-4.4%,H-2.3%,W-1.2%) than are whites.

Why? Is it racial discrimination? Are they just less polite? Does the color of the policeman's skin have any bearing on the matter?