Curious II Wrote:
-------------------------------------------------------
> Could 4 cars be run with the opening of only the front door to platform of the rear > car while the back door could be kept closed

And hence we have discovered the problem of designing commuter rail lines to the vehicle (a DMU) rather than design the vehicle to the line.

Just like WES, a very similar operation a few hundred miles to the north in the Portland Metro area, SMART is confined to a three car, single-level vehicle. The only way you can expand operations is by adding more trains, or going to another vehicle but also having to destroy and rebuild every station platform in the process. (WES is restricted to two car trains due to platform length, PLUS a designed weight limitation at the Beaverton Creek bridge at Beaverton Transit Center). Fortunately for WES, the ridership after eight years is such that one car is overkill and the entire ridership could easily fit into a regular TriMet bus with space to spare - but we MUST cater to the "I won't ever ride a bus!!!" crowd despite the operating cost for WES being 700% that of a bus rider, and the fuel economy half that of a bus.

Look at CalTrain - 100 plus years old, and they have easily expanded operations by going to bi-level coaches, adding a 6th coach, now electrification (which will actually enable them to go 7 coaches within the same footprint of a 6 car train, but many platforms will easily support much longer trains). Even Metrolink can easily support longer trains thanks to sharing of tracks and platforms with Amtrak. But when you design a system around a DMU, you aren't designing a system for the riders. If SMART is to be successful, it has to go where people want to go, and be able to accommodate that growth - design the facility so that platforms can be easily modified; train equipment can be switched out. Else, once the trains become unreliable, you will lose ridership - a victim of your own success. Much like Los Angeles' Orange Line, another system built for buses, and as a result is limited to buses. But the ridership outstrips the capacity of a bus.