Back in the 1950s there were a few nuclear-powered concept cars, such as the Ford Nucleon and Simca Fulgur. Of course they weren't remotely practical as the weight of the shielding around a reactor would have been prohibitively heavy. And you can just imagine traffic reports... 'there has been an accident at the corner of Flinders and Elizabeth Streets; motorists are advised to avoid Victoria" (credit to Tony Davis about 25 years ago on that one, from his column in Modern Motor magazine)