“Public road authority” as used in this chapter means any appropriate governing body which has responsibility for the construction and maintenance of public highways. “Overpass” as used in this chapter means a grade separation structure in which the public highway passes above and across the railroad. “Underpass” as used in this chapter means the railroad passes above and across the public highway. “Highway” as used in this chapter means any public highway, road, or street maintained by the Virginia Department of Transportation or for which maintenance payments are made pursuant to §§ 33.2-319 and 33.2-366.