A boarding and/or access aid for vehicles with passenger carrying service contains a frame with two parallel side parts (4) connected by an end profile (5), contains a step plate (2) supported in the side parts (4) in such a manner that it can be retracted and extended, and contains drive means comprising a drive motor (10) for the step plate (2). According to the invention the drive means contains two drive elements (19) designed as a chain or belt and associated one of the two side parts (4), which drive elements are arranged between guide tracks (9) and outer walls (4c) of the associated side parts (4), have a driving connection to the step plate (2) and are guided over a deflection roller (18) and a drive roller (17) connected to the drive motor (10).