While most light rail, heavy rail, and streetcars are electrically powered and each car has its own electric motors, most commuter-rail trains consist of unpowered cars towed by a locomotive that may be electrically powered but is often a Diesel. Most commuter-rail lines operate on tracks shared with freight trains and typically operate only during rush hours rather than all day and evening long.
Many commuter-rail cars are double deckers, with seats on two levels. The average commuter car in 2012 had 112 seats with room for perhaps 50 more people standing. In service, they carried an average of 35 people. With fewer stops than other forms of transit, commuter rail tends to be the fastest kind of rail transit. According to the American Public Transportation Association, the average speed of heavy rail in 2012 was 32.7 miles per hour.
The cost of starting a commuter-rail line can vary widely depending on how much work is needed to upgrade existing freight-rail tracks to be suitable for passenger service. Four commuter-rail lines in the FTA’s 2015 budget cost an average of $36 million per mile, ranging from $7 million to $68 million, with the latter being mainly new construction rather than reconstruction of existing freight lines.