diesel powered, and diesel is relatively inexpensive per mile. High local utility rates (especially during periods of peak demand) and proprietary charging systems pose barriers to adoption.

Some transit planners and authors question the logic of making an 100% electric fleet a high priority. Diesel-electric hybrid busses usually get about 4mpg. Spread over 50-150 passengers, hybrid busses can be over 10 times as efficient as gas cars. A frequent, fast, and filled transit system is an effecient one. Other system improvements such as