A trolley is provided and includes at least one driven wheel and non-driven wheels. The at least one drive wheel may be moved to a position clear of the ground or to a position in which it contacts the ground with the adjacent non-driven wheels being raised off the ground. Movement between these two positions is effected by pivoting a sub-frame to which the driven wheel and the non-driven wheels are connected. During this movement, the region of the trolley above the driven wheel is first lowered and then raised slightly such that the end elevation of the support for a patient remains the same.