Looping the CTA Brown and Purple Lines

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Looping the CTA Brown and Purple Lines

Postby TomNelligan » Sat Sep 19, 2015 12:12 pm

During my most recent trip to Chicago last week I had occasion to make several rush hour L trips between the Loop and the North Side and found myself pondering the following mystery: why does the Brown Line traverse the Loop counterclockwise and the Purple Line clockwise when they both enter it at the same point? I suspect there is a reason, but it seems non-optimum that under the current arrangement inbound Purple Line trains have to wait for clearance to cross the whole plant at Lake & Wells at the busiest times of day rather than just continuing straight ahead like their Brown trackmates. Looping the Purple Line counterclockwise would also help unclog the inner Loop track at rush hour by moving more trains to the less-used outer track. But I'm an out-of-towner, so I'm probably missing something.
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Re: Looping the CTA Brown and Purple Lines

Postby MACTRAXX » Sun Sep 20, 2015 2:01 am

Tom N:

I believe that these two routes travel in opposite directions on the quads of the Loop L structure to balance
out the number of trains using each track and offer options for riders traveling between Loop L stations.

Ravenswood and Evanston Express trains (using their former line names) share track space with the Lake-
Englewood-Jackson Park trains (Green) on the north and east quads; Midway (Orange) trains travel
clockwise and Douglas trains (Pink) run counterclockwise alongside Brown and Purple Line trains
which evens out both Loop L tracks to two encircling routes for each track.

The CTA once ran a Loop Shuttle train on weekdays that ran clockwise - this service began on 9/30/69
and was discontinued on 9/30/77.

CTA's Loop L operation is a interesting balancing act and I remember that the north and east quads - which
once hosted the busy Dan Ryan route before the line terminals were changed in 1993 - were once much busier
then the south and west quads. I also remember at certain times on nights and weekends the south and west
quads would be closed but with the increase of service and routes using the Loop L in more recent years that
has changed...

See: http://www.chicago-l.org

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Re: Looping the CTA Brown and Purple Lines

Postby GWoodle » Sun Sep 20, 2015 4:39 pm

TomNelligan wrote:During my most recent trip to Chicago last week I had occasion to make several rush hour L trips between the Loop and the North Side and found myself pondering the following mystery: why does the Brown Line traverse the Loop counterclockwise and the Purple Line clockwise when they both enter it at the same point? I suspect there is a reason, but it seems non-optimum that under the current arrangement inbound Purple Line trains have to wait for clearance to cross the whole plant at Lake & Wells at the busiest times of day rather than just continuing straight ahead like their Brown trackmates. Looping the Purple Line counterclockwise would also help unclog the inner Loop track at rush hour by moving more trains to the less-used outer track. But I'm an out-of-towner, so I'm probably missing something.



From a passenger point of view the routing helps distribute you to the final destination in the Loop. Coming from the South, Orange line passengers can get off & swap to a Green Line train at Roosevelt Road. From there may be a short wait for the final dash to the east/north leg. Otherwise you have to wait to get around the loop to get back to the same State/Lake station.

Coming from the North it gives passengers the same options. You also may have the ability to not overload a State/Lake platform for northbound passengers.
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Re: Looping the CTA Brown and Purple Lines

Postby Allouette » Tue Sep 22, 2015 7:00 am

The Brown/Purple service pattern dates back to the 1969 change in service when the Dan Ryan line opened. From the late 1950s after the Congress line opened until 1969, Lake trains ran counterclockwise on the inner loop, and Ravenswood and Evanston trains ran counterclockwise on the outer loop. During the middle of the day and on weekends Ravenswood trains ran counterclockwise on the inner loop as well, crossing over near tower 18. The change from Lake to Lake/Dan Ryan made the inner track clockwise. The idea at the time was that running Evanston trains, which were rush hour only, clockwise on the inner track balanced the traffic load on the Wabash and Lake legs of the loop. The rest of the time when Evanston trains weren't running, the loop shuttle ran clockwise about 16 hours a day - not quite around the clock. Adding the Orange Line trains to the inner track allowed removal of the loop shuttle. Today's track arrangement is much more flexible than in the past, but traditions die hard.
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