49 CFR Parts 37 & 38 - Department of Transportation (DOT) ADA Regulations

(d) Coordination with boarding platform—

(1) Requirements. Cars operating in stations with high platforms, or mini-high platforms, shall be coordinated with the boarding platform design such that the horizontal gap between a car at rest and the platform shall be no greater than 3 inches and the height of the car floor shall be within plus or minus 5/8 inch of the platform height. Vertical alignment may be accomplished by car air suspension, platform lifts or other devices, or any combination.

(2) Exception. New vehicles operating in existing stations may have a floor height within plus or minus 11/2 inches of the platform height. At key stations, the horizontal gap between at least one accessible door of each such vehicle and the platform shall be no greater than 3 inches.

(3) Exception. Where platform set-backs do not allow the horizontal gap or vertical alignment specified in paragraph (d)(1) or (d)(2) of this section, car, platform or portable lifts complying with §38.95(b) of this part, or car or platform ramps or bridge plates, complying with §38.95(c) of this part, shall be provided, ensuring compliance with section 37.42, where applicable.

(4) Exception. Retrofitted vehicles shall be coordinated with the platform in new and key stations such that the horizontal gap shall be no greater than 4 inches and the height of the vehicle floor, under 50% passenger load, shall be within plus or minus 2 inches of the platform height.