A motorist whose vehicle straddles two traffic lanes, as in Stay in your own lane, you road hog! This expression uses hog in the sense of "a greedy or selfish person." [Colloquial; late 1800s]
An inconsiderate (usu. obstructive) driver or cyclist. (1891 —) . K.Bonfiglioli 'Lost my temper....Bloody road hog.' 'He might easily have done us a mischief,' I agreed (1972).