MBTA Blue Line - Track Crossover Between State and Government Center

[Elmer]

I was surprised tonight when MBTA station attendants at the Government
Center Blue Line platform (Scollay Under) were directing passengers to
the Inbound track for service to Wonderland. I didn't think there was
a track crossover between GC and State. In fact, the plans for
connecting the Blue Line to the Red Line at Charles station call for
installation of a new crossover between GC and State.

But sure enough, as the train departed Government Center (towards
Wonderland, on the track that's normally Inbound towards Bowdoin) it
crossed over to the Outbound track before arriving at State. The
obvious question is, why isn't this the normal mode of operation
whenever Bowdoin station is closed instead of always looping every
train (with no passengers) all the way to Bowdoin and back?

Elmer

[Martin Edwards]

Post by Elmer
I was surprised tonight when MBTA station attendants at the Government
Center Blue Line platform (Scollay Under) were directing passengers to
the Inbound track for service to Wonderland. I didn't think there was
a track crossover between GC and State. In fact, the plans for
connecting the Blue Line to the Red Line at Charles station call for
installation of a new crossover between GC and State.
But sure enough, as the train departed Government Center (towards
Wonderland, on the track that's normally Inbound towards Bowdoin) it
crossed over to the Outbound track before arriving at State. The
obvious question is, why isn't this the normal mode of operation
whenever Bowdoin station is closed instead of always looping every
train (with no passengers) all the way to Bowdoin and back?
Elmer

Make da wrong choice an' you gonna end up in B'more, know wham sayin'

[John Levine]

Post by Elmer
But sure enough, as the train departed Government Center (towards
Wonderland, on the track that's normally Inbound towards Bowdoin) it
crossed over to the Outbound track before arriving at State. The
obvious question is, why isn't this the normal mode of operation
whenever Bowdoin station is closed instead of always looping every
train (with no passengers) all the way to Bowdoin and back?

Probably pathing. If they're going to use the crossover, they are
basically making GC a single track station, and an inbound train
would have to wait for an outbound train to get out of the way.
If they use the loop, both tracks are always available, and if the
trains get bunched up, they can hang around in the loop and wait.

Even assuming the crossover is an X, so they can bring trains into
either side, they still have to schedule it.

R's,
John

[Elmer]

Post by John Levine

Post by Elmer
But sure enough, as the train departed Government Center (towards
Wonderland, on the track that's normally Inbound towards Bowdoin) it
crossed over to the Outbound track before arriving at State. The
obvious question is, why isn't this the normal mode of operation
whenever Bowdoin station is closed instead of always looping every
train (with no passengers) all the way to Bowdoin and back?

Probably pathing. If they're going to use the crossover, they are
basically making GC a single track station, and an inbound train
would have to wait for an outbound train to get out of the way.
If they use the loop, both tracks are always available, and if the
trains get bunched up, they can hang around in the loop and wait.
Even assuming the crossover is an X, so they can bring trains into
either side, they still have to schedule it.

Scheduling can not be the reason. Except during rush hour (when Bowdoin is open anyway), there's never more than one train inbound of State. Otherwise, if you're waiting at GC, it's always the same inbound train that comes back 'round to the outbound side after looping (empty) at Bowdoin. You can also watch it on the real-time display at the Scollay Under platform.

I rode in the front car today to get a better look at the crossover. It's right at the curve where the tracks separate before entering the (center platformed) Government Center station. It's also not an X crossover; inbound trains can't switch to the outbound side when entering GC, but they can reverse direction and switch to the other side when going back out.

So, I can understand why a new crossover would be needed when Bowdoin is eliminated and/or closed for construction of the extension to Charles; it would then be needed to handle the rush hour schedule and for staged trains to park on the other side of GC.

Currently though, other than the driver not having to walk to the opposite end of the train, I still don't see any advantage to making every train always loop all the way around Bowdoin with no passengers.

Elmer

[Jimmy]

Post by Elmer
Scheduling can not be the reason. Except during rush hour (when Bowdoin is open anyway),
there's never more than one train inbound of State.

What if a train is late, so trains get bunched together? That happes
fairly often on the Red Line, even outside rush hour.

Do you happen to remember how fast the train went across the
crossover?

After the Alewife crossover derailment in December 2009, they lowered
the speed limit from 25 to 10 in that area. Subsequent signal work
shortened the slow zone, and allowed trains going straight through
(rather than crossing over) to go 25, but it's still 10 for trains
switching tracks. It's no fun wasting an extra minute crossing over,
especially on a train that's already late.

So I was surprised when a train crossing over at Harvard during the
weekend track work went 25.

What are the speed limits on other MBTA crossovers? What's typical in
other urban rail systems?

Post by Elmer
I rode in the front car today to get a better look at the crossover. It's right at the curve where the
tracks separate before entering the (center platformed) Government Center station. It's also not
an X crossover; inbound trains can't switch to the outbound side when entering GC, but they can
reverse direction and switch to the other side when going back out.

http://www.mbta.com/uploadedfiles/documents/Bluebook%202009.pdf
(warning: big file) has track maps starting on page 25 (though they're
not to scale).

Why does the multimillion dollar in-station announcement system say
"The next Blue Line train to Bowdoin is now approaching", even during
the hours trains terminate at Government Center?

Jimmy