Abstract: A road/rail vehicle has front and rear road wheels, an engine driving the rear road wheels, and an indicator of actual vehicle speed. Retractable front and rear rail wheels are mounted on the vehicle and movable from a raised road position for operation in a road mode to a lowered rail position where the rail wheels engage rails of a railroad track for operation in a rail mode. A suspension system is adjustable in the rail mode to vary a weight proportion of vehicle weight that is a tractive weight carried by the rear road wheels and a guidance weight carried by the rear rail wheels, and a suspension control is adjusts the suspension system to provide a selected weight proportion. A maximum allowable vehicle speed decreases as the tractive weight increases and a maximum speed indicator shows the maximum allowable vehicle speed for the selected weight proportion.