Conveyor comprising an elongated flat support with a belt positioned thereon. Driving of the belt takes place by friction as a consequence of the contact force between the belt and a drive roller, which contact force increases on motion and is initiated by a low force with which said belt is pressed onto said drive roller by a pressure roller at the location where the return part of said belt leaves said drive roller. Apart from a very low contact force for starting the movement, contact pressure is applied only during driving, the contact force being proportional to the driving force of the conveyor that is actually required. According to the invention there are two pressure rollers located on either side of the drive roller, the movement of said pressure rollers being linked in such a way that when one pressure roller is moved away from the belt by the force generated by driving the belt the other pressure roller is moved towards the belt and thus provides the initiating contact force between conveyor belt and drive roller.