DutchRailnut wrote:even electric locomotives use less power than entire train of EMU's, that's why their slower.
Slower to accelerate anyway. And given enough cars and enough distance between stops, it becomes more efficient weight-wise to use a single locomotive to pull a train than it does to use EMUs. That's why Amtrak has invested so heavily in locomotives, and probably why they didn't order more Metroliner-based regional equipment along with Amfleets (that and the price.)
On the other hand, commuter service and heavy rapid transit need redundancy, light weight, and quick acceleration to maintain a tight schedule, and the more standard they can make their infrastructure the better. Locomotives eat up the track as compared to MUs, just like one semi destroys roads much faster than a fleet of pickups carrying the same cargo, and a subway system can't easily take an entire line out of service for repair.