Abstract: A public transit vehicle is driven by a hybrid drive system including a diesel engine, a generator driven by the engine, two battery packs for storing energy from the generator and from re-generated braking energy and a transmission in the form of a motor driven by the electrical energy from the generator and/or the batteries. The drive components are mounted on a sub-frame for carrying which is arranged for readily releasable attachment to the main longitudinal beams of the vehicle body so as to be carried on the vehicle body during operation of the vehicle. The sub-frame itself is designed simply and avoiding duplication of support elements so that it is incapable of supporting by itself the radiator and the transmission which are partially supported in use by elements of the vehicle body.