Road/rail vehicle with tractive weight control

A method of operating a road/rail vehicle to ensure engagement of rear rail wheels thereof with rails of a railroad track, the method comprising:

• providing a vehicle with front and rear road wheels, an engine operative to drive the rear road wheels, and displaying actual vehicle speed at an operator's station;
• mounting retractable front and rear rail wheels on the vehicle such that the front and rear rail wheels are movable from a raised road mode position, where the rail wheels are above a road surface, to a lowered rail mode position;
• with the rail wheels in the road mode position, maneuvering the vehicle into alignment with rails of a railroad track;
• moving the front and rear rail wheels down to the rail mode position to engage the front and rear rail wheels with the rails;
• manipulating a suspension control at the operator's station to activate an adjustable suspension system to exert a downward force on the front and rear rail wheels and manipulating the suspension control to achieve a selected 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;
• determining a maximum allowable vehicle speed for the selected weight proportion so that the guidance weight provides sufficient downward guidance force to ensure engagement of the rear rail wheels;
• displaying the maximum allowable vehicle speed;
• and
• operating the vehicle at an actual vehicle speed no greater than the maximum allowable vehicle speed.