Blue Line engineering question

Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

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Postby ckb » Fri Apr 23, 2004 4:17 pm

Having taken the Blue Line to the airport many times, I think that curve at State is the real clearance restriction and unless it is re-engineered a trip to Lynn on the Blue Line would be a long slow one.

I'm missing something here - how does that curve affect train speeds further out on the Blue Line? I would think it only affects the train car size and the speed around that curve.

I remember the shops at Harvard, but they were on the Cambridge side of the river. Right where the Brattle Street crosses Mem. Drive, not next to the stadium.

Thanks for the clarification. Its hard to imagine shops in that area now with the development there.

There were tracks across the Charles to the Stadium, though, right? I thought I remembered reading that they ran cars there on game days.

Postby jrc520 » Fri Apr 23, 2004 7:51 pm

The curve radius means you have to move slowly around the curve. Which spreads to the whole line. so yes, it does slow things down.

The tracks ran on the bridge only. right before the portal on the kendal side, they turned onto the redline tracks.
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Postby JayZ » Sat Apr 24, 2004 9:59 am

I disagree. The speed with which the curve can be taken depends on many aspects, not just the radius of the curve. Blue line trains take the State St. curve faster than Red Line trains take the Harvard curve, though that one (the Harvard curve) is less tight than the State Street curve. I think it has to do with the fact that the cars are smaller, plus the fact that the blue line doesn't have ATS, so operators hardly ever observe the 8mph speed limit :)

Postby jrc520 » Sat Apr 24, 2004 11:02 am

the bowdin curve is also a lot more to go through. you have a small quick change or direction @ state, but bowdin is a massive loop. plus, bowdin is not like state. state has no signal on each end of the curve. bowdin does. those signals are also what's jamming things up.
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Postby Leo Sullivan » Tue Apr 27, 2004 8:42 am

To answer ckb's exact question-
If the curve costs an extra 12 seconds then, that is 12 seconds added to the running time of the entire line. Since the state St. Curve is 'on the line' rather than being a terminal loop, that time goes directly onto the total. That is the only direct effect. The real problem is that the physical restrictions of the curve may lead to car design limitations, slowing loading/unloading, over the entire line, and generally discouraging cars suitable for long distance, high speed operation. As noted above, the North Shore Line dealt with this pretty effectively but, design rituals were less restrictive 80 years ago.
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Postby ThinkNarrow » Thu Apr 29, 2004 9:22 am

There were tracks across the Charles to the Stadium, though, right? I thought I remembered reading that they ran cars there on game days.

In response to ckb's question about tracks to Harvard Stadium, the Eliot Yard contained a passenger platform adjacent to what is now JFK Blvd. The wall that separated the yards from JFK Blvd had sections that rolled away to allow access to/from the platform. This was referred to as "Stadium Station," and game day trains could proceed beyond Harvard Station to Stadium Station, from which it was only a short walk across the Charles to the stadium. The tracks did not cross the Charles, only the pedestrians who disembarked at Stadium Station.
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Postby ckb » Thu Apr 29, 2004 11:42 am

Cool -- thanks for the answers, guys.

I guess I understand now that it seems the biggest problem with tight turns on the Blue line is the design of equipment (certainly can't buy an "off-the-shelf" product to run there), but it still seems possible to me to run a very efficient service even with a tight turn here or there - after all, a shorter car should actually be lighter and therefore easier to accelerate. Yes, there are then capacity issues with smaller than normal cars, but since we're talking about a line that runs 4-car operation presently .... (I know we're working towards six - but even then the limitation will be on the platform length at each station rather than car design).

Re: Stadium station, thanks for the clarification. With the development and the J.F.K School of Harvard now in that area of Harvard Square now, it is hard to imagine transit yards and shops!


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