A track displaceable service vehicle replaces individual worn or damaged idlers with new idlers in the upper run and lower run of a belt conveyor with rising or falling conveying route, in which there is little space for the use of the service vehicle for replacing the idlers. The service vehicle accommodates a magazine for new and worn idlers and auxiliary devices for lifting the belt and removing old and for installing new idlers. A platform carries service personnel, and can be brought into a horizontal position in case of an inclined travel route of the service vehicle. The replacing of worn or defective idlers takes place in certain cycles in which the entire segment of the belt conveyor is removed and all worn and defective idlers are replaced. The service vehicle has a drive and is suitable for long tunnel sections (conveying routes which extend over several kilometers).