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.
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" onclick="window.open(this.href);return false;
MACTRAXX