Alternative forms of motive power for suburban rail rapid transit

Several forms of motive power are described that could offer much lower implementation costs for suburban rail rapid transit. The same concepts could apply to suburban electrified commuter railroads where electric operation is mandatory on critical center city terminal portions of a system. The proposed alternatives for heavy (i.e., high platform) rapid transit ought to have costs on the order of those usually associated with light rail transit while still providing the spaciousness and comfort associated with suburban heavy rail rapid transit. The unconventional motive power units described are intended to allow extension of existing (or proposed) electric rail transit into distant suburbs using nonelectrified railroad tract that may be abandoned or occasionally used by a freight train.>