Railplanes operate at speeds similar to racing cars and just like racing cars they have spoilers– so called because they are designed to spoil any lift that might be generated by the vehicles moving through the air. In this capacity, spoilers are wings that push down.
The wings of an aircraft provide stability in addition to lift. The spoilers of a railplane function in the same capacity by augmenting the stability provided by the suspension. When a vehicle encounters a heavy crosswind, the spoilers act as control surfaces to counter the buffeting caused by the wind.