Bart cars are electric. Electric current is delivered to the trains over a third rail. A third rail is a method of providing electricity to power a railway through a continuous rigid conductor alongside the railway track or between the rails.
eBART originally intended to use the existing Union Pacific (UP) line that runs from Pittsburg to Tracy. Options included purchasing the line from UP or leasing the line. In a feasibility study, from 2002, DMU technology emerged as the preferred option for the eBART. There were a number of reasons: DMUs are more rugged than light rail; conventional BART requires more costly engineering, vehicles, stations and systems, and has a project cost three times that of the DMU trains.
So, what exactly is a DMU? It is a lightweight, self-propelled passenger railcar that runs on diesel fuel. It can carry roughly 135 people and can reach up to 75 miles per hour maximum speed. DMUs can be operated singularly, or with any number of units coupled together and controlled by a single operator. They can have a cab at both ends, the train can be reversed without having to uncouple/re-couple and move the locomotive, which results in far quicker turnaround times.