Definition of "motorable"

During the Cultural Revolution, Taipai County built 44 roads, increasing the length of motorable road by 360 kilometers.

1974 June 6 , “Briefs: Shensi County Road-Building”, in Daily Report: People's Republic of China‎, volume I, number 110, Foreign Broadcast Information Service, page M 1‎

And when finally I got to the end of the five-hour drive over the highest motorable pass in the world, it was to learn that the gompa in Hunder was closed.

2009 March 13, Pico Iyer, “Heaven’s Gate”, in New York Times‎