In a blended HSR + Caltrain system, slowly transitioning to full grade separation over a time scale of decades, several constraints exist that will impede Caltrain's ability to add capacity to meet increasing ridership demand:
- More trains per hour won't work. Because there are only two shared tracks, the capacity of the corridor (as measured in trains per hour) is limited. It's going to be a stretch for Caltrain to operate six trains per hour per direction with HSR in the mix, so adding more is clearly out of the question until the much-dreaded additional tracks are built.
- Longer trains won't work. Train length is limited at stations such as Burlingame and Menlo Park, where grade crossings are found at both ends of the station platforms. Until these locations are grade-separated and new longer platforms are built, adding more cars to make longer trains is not feasible. In any case, most Caltrain platforms limit train lengths to 600 feet (or 7 standard-length cars), at least until they are rebuilt.
- Taller trains won't work. Today's bi-level trains already take good advantage of the available height, so there is no seating capacity to be gained by growing trains any taller.
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Russia / USA / Europe
The Advantages of Extra-Wide EMUs
The diagram below shows a cross section of three double-deck trains: a traditional European EMU of the sort coveted by Caltrain; a Caltrain Baby Bullet car; and a hypothetical extra-wide EMU with comfortable five abreast seating, a few inches wider than the Russian model described above.
- More passengers per train. With five abreast seating, 15 to 20% more seating can be provided without increasing train length or train frequency. Even in those areas without seats, more floor space is available for standees.
- More usable space. Extra width makes for more spacious and comfortable vestibules, stairs, and passageways between cars. High-traffic areas near doors, bicycle racks, restrooms, and luggage racks do not impede the flow of passengers.
- Lower crew costs. The number of conductors required on a train is dependent on the number of cars in the train. Under the present labor agreement, there is a strong incentive to keep train lengths to six cars and to maximize passenger capacity per car. Five-abreast seating reduces the crew cost (and other operating costs) per available seat.
- Future-proof HSR compatibility. Because the CHSRA has already settled on a single-level train architecture for its high-speed trains, it is likely that similar capacity limitations will drive the future California trains to be extra-wide, like the Japanese Shinkansen or the Russian Velaro. Converting Caltrain to a wider standard helps achieve future platform interface compatibility with HSR, which is not just a matter of height but also of width.
- Easier conversion to high platforms. Wider trains can be fitted with both high and low doors to accommodate a platform transition period, without cutting as badly into the seat count as for a normal size train. (The Russian example is built exclusively for high platforms, but more doors could be added on the lower level.) What's more, with high platforms built further away from the tracks, those annoying freight trains get a little bit more clearance.
- Easier vehicle packaging. From an engineering standpoint, modern EMUs are like a jigsaw puzzle where every vehicle component must find its place under multiple constraints. More width gives vehicle designers more flexibility to make everything fit, making trains more comfortable and maintainable.
Caltrain should make full use of the generous clearances available on the peninsula corridor. In a blended future where HSR limits the number of peak-hour commuter trains, extra-wide EMUs with five-abreast seating are an attractive solution for giving Caltrain more rush-hour capacity.
[Update 08/2014: this Swedish academic paper analyzes the numerous advantages of extra-wide trains in far more detail, going into cost elasticities etc.]