 , several manufacturers were working on new hybrid designs, or hybrid drivetrains that fit into existing chassis offerings without major re-design.A challenge to hybrid buses may still come from cheaper lightweight imports from the former Eastern bloc countries or China, where national operators are looking at fuel consumption issues surrounding the weight of the bus, which has increased with recent bus technology innovations such as glazing, air conditioning and electrical systems.A hybrid bus can also deliver fuel economy though through the hybrid drivetrain.