WordNet (r) 3.0 (2006):

road hog
    n 1: a driver who obstructs others [syn: road hog, roadhog]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "road hog":
   Sunday driver, backseat driver, bus driver, busman, cabby,
   cabdriver, careerist, chauffeur, driver, egotist, fortune hunter,
   hack, hackdriver, hackman, hacky, hit-and-run driver, hog,
   individualist, jitney driver, joyrider, lone wolf, loner,
   monopolist, motorist, narcissist, self-advancer, self-pleaser,
   self-seeker, self-server, speeder, taxidriver, teamster,
   temporizer, timepleaser, timeserver, truck driver, trucker,
   truckman, tufthunter