Electric locomotives would save some money but deliver much less benefit than the â€œelectric multiple unitsâ€ (EMUs) that Caltrain has been planning to purchase, according to transit bloggers Alon Levy and Clem Tillier.
Given the risk to the $647 million in federal funding for Caltrain electrification, several readers ask whether electric locomotives would be a reasonable backup plan. Caltrainâ€™s plan to electrify the line uses â€œelectric multiple unitsâ€ – rail cars that are each separately powered by overhead electric wires. Another way to electrify is to buy electric locomotives and to use them to haul the current set of cars.
This approach would save some money. Currently, Caltrain has budgeted $551 million for EMUs. Research by reader Michael Gimbel suggests that Caltrain would save about $400 Million by purchasing electric locomotives such as the Siemens ACS-64 â€œSprinter.â€ However, according to Levy and Tillier the savings would be substantially less, because Caltrain would still needs to replace the over-30-year-old gallery cars that are nearing the end of their useful life. Replacing the gallery cars would cost about $200Million extra.
Meanwhile electric locomotives would have much less benefit. The main performance benefit of electrification is faster acceleration that lets the system reach more stops in the same or less time, which is especially useful in a heavily populated metro like the Bay Area, with stops every couple of miles.
While a Sprinter is pretty powerful and has good acceleration at medium speed, the acceleration is poor at low speeds, so they would provide only half of the time savings. To quote Alon Levyâ€™s explanation:
â€œA EuroSprinter lugging 6 Bombardier BiLevel Coaches has a power-to-weight ratio of 16.5 kW/t (6-car KISS set: 20.3 kW/t maximum 13.5 continuous). But they are still crummy at low speeds, because maximum acceleration at low speed is limited by adhesion, which in turn is a function of the proportion of the load that is supported on powered axles. This proportion is somewhere in the 35-45% region for the KISS and 22% for a Sprinter pulling 6 BBCs. At 0.5 m/s^2 initial acceleration, the acceleration + deceleration penalty to 130 km/h is around 75 seconds; I don’t know what the KISS’s penalty is, but the FLIRT’s is 35, and the KISS is almost as powerful as the FLIRT. This is around half the travel time saving from electrification.â€
What is worse, by keeping the current unpowered car design, Caltrain would not be able migrate to level boarding, which lets passengers get on the train more quickly without stairs, faster for everyone, and more accessible for people with mobility challenges, luggage, and bikes. Level boarding will provide half again as much speed benefit as electric power with EMUs. Caltrain has been planning to migrate to level boarding with the new electric cars, by changing platforms over time.
So, electric locomotives would save Caltrain about $200Million, while providing only about a third of the benefit of electrification with EMUs, and locking in slower speeds and less accessibility for another 30 year replacement cycle.
Caltrain, the region, and the state would be better off finding backup funding to deliver the project in a way that would deliver the benefits including speed, level boarding, and service to the corridor station areas that are seeing transit-oriented development.
Update: here is more analysis by Clem Tillier showing why EMUs are best for the Caltrain corridor.