boblothrope wrote:Choo Choo Coleman wrote:
The Postal Service had planned to relocate to South Boston and hand over the mail-sorting facility to a private developer that was planning to build a large mixed-used complex on the 16-acre site. That redevelopment would have also cleared the way for the MBTA to acquire more land in the area to add tracks for expanded commuter rail service.
Have the people planning the South Station expansion taken a look at current operating practices? I suspect they could find ways to turn trains significantly faster, to get more capacity out of the existing tracks.
Not really. You have 13 platform tracks for 9 MBCR lines and 3 Amtrak lines (2 of them running very frequently). And more importantly, 13 platforms for 9 mainline tracks heading into the station from the NEC, Worcester, Fairmount, and Old Colony lines with a very quick line split a few hundred feet from the platforms (5 NEC+Worcester tracks abruptly peeling westbound with 4 Fairmount+Old Colony tracks continuing southbound). This keeps trains segregated to certain platform berths within ~2 tracks of the mainline track it comes in/out on, because that's less time spent crossing over tracks and fewer trains that have to be held while one is crossing over. While it is possible for any train to use any platform, it gums up the whole works to have one cutting across multiple crossovers and cutting across another line's lead tracks. This is why Old Colony trains are never on the Atlantic Ave.-side platforms and Worcester trains never next to the Post Office. The highest-risk area for collisions is within yard limits, as last month's Washington Union Station MARC--Amtrak fender-bender that hosed the entire NEC can attest. You wouldn't be able to have multiple trains entering or exiting South Station at the same time if any platform were fair game; you'd have backups as only one can move from the platforms at once. You can move 'em simultaneously if the concurrent arrivals/departures are on lines that are never at risk of crossing over each other's oncoming paths within yard limits. i.e. an Old Colony and a Worcester train can go in at the same time since they'll be several tracks apart at all times, and probably an NEC train too sandwiched in the middle if the right combo of platforms are unoccupied. The current setup
is the single-most efficient way of maximizing headways.
What the extra tracks allow is for punting the Old Colony and Fairmount berths onto the additional platforms for breathing room in the expansion space, and then letting the NEC and Worcester line spread out to take up almost all of the existing platforms. That keeps the line segregation intact while opening up more platforms for rapid-transit level Fairmount service, substantially increased Worcester service, enough NEC slots just to keep up with current growth, and then the future capacity for Fall River/New Bedford via NEC, Millis via NEC, and Cape via Old Colony (the capacity bump would be enough for all those services, whether they ever get built or not). To juggle just the Worcester, Fairmount, and NEC increases within current track capacity is going to mean crossing more trains over during rush hour, and the more they do that the fewer trains they'll be able to simultaneously move within yard limits. Past that sort of tipping point increased traffic actually
limits capacity.
