OSHA Requirement 1910.178(k)(1) that states "The brakes of highway trucks shall be set and wheel chocks placed under the rear wheels to prevent the trucks from rolling while they are boarded with powered industrial trucks.
Two wheel chocks, mounted in readily accessible locations, each designed to hold the fully loaded apparatus on a 10 percent grade with the transmission in neutral and the parking brake released.
Chocks that meet or exceed 1901 Recommendations
10-2(1)* Two wheel chocks, mounted in readily accessible locations, which on hard surface, one will hold the fully loaded fire apparatus on a 15 percent grade and two will hold the fully loaded apparatus on a 30 percent grade. The bottom surface of the wheel chock is to be solid.
Chocks that meet or exceed 1906 Recommendations
OSHA RR Chock Recommendations
OSHA REGULATIONS §1910.110 (15); 1910.111 (13); 1910.30 (A) (5) OSHA REGULATIONS Require that car brakes are applied and a wheel chockis in place before a car can be safely worked. Set the car brake first and then install the wheel chock. A chock alone will not hold the car. Use two chocks per car being chocked.If your track has a dip or hollow, you may have to take additional precautions.