An apparatus for road vehicles includes a sealed housing (07) which mounts the shafts (11 & 12) in bearings (10). Closed chain or belt loops (13) are driven by sprockets or pulleys (29) which are supported on the shafts (11 & 12) by one direction clutch bearings (09) such that the shafts (11 & 12) can only transmit power in a single direction (15). A multiple array of active elements (14) are activated by the vehicle wheels and have suitable means or geometry such that they transmit force to cause displacement of the chains or belts (13) and drive a generator (06) when activated but slip in the opposite return direction independently and without further effect to the chains or belts (13). A gearbox (28) may be used to change the shafts orientations. A multiple of chain or belt loops (13) are mounted to the shafts (11 & 12) at a suitable spacing in a direction perpendicular to the vehicle travel direction (04). The active elements (14) have means to bias them to return to their non-activated position after activation. The active elements (14) may operate further active elements having a means of one direction transmission of force to cause the chains or belts (13) to displace.