where it crosses the tracks should be level with the top of the rails. For a distance of 30 feet on each side of the
crossing, the highway approach should be no more than 9 inches below nor more than 3 inches above the level of
the rails. This insures that approaches are on a smooth grade so that vehicles with low road clearance may pass
over the crossing without their undercarriages touching either the rails or road surface, and no vehicles are jolted
in making the crossing. Flangeways, or passageways for the wheel flanges, 2 1/2 inches wide between the gage
side of rails (RT 670, par. 1.6a) and the roadway must be provided, unless curvature of the railroad is more than 8
degrees. If more than 8, the flangeways should be 2 3/4 inches across. For both, the minimum depth of the
flangeway should be 2 1/2 inches. The crossing should be about 4 feet wider than the road itself.
Crossings may be constructed of various materials and in different designs; the choice depends upon the
amount and kind of highway traffic and the materials available. Materials include rails, wooden planks, asphalt,
concrete, precast concrete slab, or prefabricated metal planks. Figure 4.1 illustrates two types of highway grade
crossings, one with wooden planks and asphalt and the other with wooden planks only.
A simple crossing may use 3-inch wooden planks spiked to blocks on both sides of each rail. The outside
ones are placed flush against the head of the rail, while those inside are set to provide the necessary flangeway
between the planks and the gage side of the head of the rail. The space between the inside planks may be filled
with cinders, gravel, concrete, planks, or asphalt. A similar crossing uses rails instead of planks inside the
running rails. The ends of the inside rails are bent toward the center of the track to provide a 4-inch flangeway
opening. The rails may be placed on their sides with their heads against the web of the running rails, or they may
be placed on their bases with separators to maintain the proper flangeways.
Good drainage is especially important to the proper maintenance of highway grade crossings. The
culverts substituted for main side ditches under the highway approaches must be kept clean and free flowing.
Cross lateral drains may be necessary, and water flowing on the highway should be diverted before it reaches the