D.C. Mun. Regs. tit. 24, r. 24-3103
The minimum side clearances from the center of tangent standard gauge railroad tracks that are used or proposed to be used for operating freight cars shall be as prescribed in this section, except as otherwise prescribed in this chapter.
On all structures and obstructions above the top of a rail, except those specifically mentioned, the side clearances shall be not less than eight feet by six inches (8 ft. x 6 in.).
To further reduce occupational hazards, posts, pipes, warning signs, and similar obstructions shall have a side clearance of ten feet (10 ft.), where practicable.
Platforms that are eight inches (8 in.) or less above the top of a rail shall have a side clearance of not less than four feet by eight inches (4 ft. x 8 in.).
Platforms that are more than eight inches (8 in.), but not more than four feet (4 ft.) above the top of the rail, may have a side clearance of not less than five feet by seven inches (5 ft. x 7 in.); Provided, that where these platforms are used for loading or unloading freight cars, a side clearance of not less than eight feet by six inches (8 ft. x 6 in.) is maintained on the opposite side of the track to any fixed structure or that the track center to an adjacent track is not less than fourteen feet (14 ft.).
Where side clearances are less than eight feet by six inches (8 ft. x 6 in.), as authorized by this rule, warning signs directing attention to the reduced clearances shall be erected at suitable locations, except where the platform is used principally in loading and unloading passenger cars.
Platforms previously constructed with clearances less than are prescribed in this chapter may be extended with lesser clearances, unless the extension is connected to the reconstruction of the original platform.
Through bridges supporting tracks, tunnels, water columns, and oil columns shall be not less than eight feet (8 ft.) from the center line of the track.
Clearances for through bridges supporting tracks, water barrel platforms and refuge platforms on bridges and trestles not provided with walkways, hand rails, water barrels, water columns, oil columns, block signals, when all or portions thereof are four feet (4 ft.) or less above the top of the rail may be decreased to the extent defined by a line extending diagonally upward from a point level with the top of the rail and five foot (5 ft.) lateral distance from the center line of the track to a point four feet (4 ft.) above the top of the rail and an eight foot (8 ft.) lateral distance from the center line of the track; Provided, that the minimum clearance for hand rails and water barrels on bridges with walkways shall be seven feet by nine inches (7 ft. x 9 in.).
Switch boxes, switch-operating mechanisms, and accessories necessary for the control and operation of signals, and interlockers projecting four inches (4 in.) or less above the top of a rail, shall have a side clearance of not less than three feet (3 ft.).
The center spindle of signal and switch stands three feet (3 ft.) or less above the top of the rail, and located between tracks where not practical to provide clearance otherwise prescribed in this chapter, shall be not less than six feet (6 ft.) from the center line of the track.
Side clearances, on sidings only, at entrances to and inside warehouses and industrial buildings shall be not less than eight feet (8 ft.) from the center line of the track; Provided, that this rule shall not supersede or affect the clearances in § 3103.3.
All minimum side clearances prescribed in this section are for tangent tracks. Structures adjacent to curve tracks shall have an additional minimum side clearance compensating for the curvature.
D.C. Mun. Regs. tit. 24, r. 24-3103