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Blue Line Needs Better Signals, More Electricity, Articulated Trains to Alleviate Crowding

A new study from the Chicago Transit Authority on 'L' capacity highlights where trains are running at capacity, and how the CTA can alleviate crowding. We'll focus on the Blue Line's O'Hare branch since that is where is a lot of new TOD developments are being built –and many have already opened – causing some existing residents, and the airports commissioner, to be concerned that the new residents will escalate a crowding issue.

The study [PDF] showed that the Blue Line along Milwaukee Avenue is "at capacity" between Western and Clark/Lake inboundin the morning, and "nearing capacity" between Clark/Lake and Washington. The Blue Line has "available capacity" everywhere else.

map of passenger crowding in the morning inbound rush hour
Map shows "at capacity" line segments in red across the CTA 'L' system, going toward downtown, during the 6-9 AM rush hour.

The constraints, or "weakest links", as the study calls them, are a lack of electricity supply between Harlem and Grand stations that is necessary to power additional trains, long passenger boarding times at Clark/Lake, and a limitation of the signals around Clark/Lake.

The study listed some possible solutions that would require further study. Across the system, switching to a new signaling system could increase capacity on all lines. Currently, the CTA uses a fixed-length block signal that means each train virtually occupies what can be a very long section of track, sometimes putting two train lengths in between two trains. By using a moving block signal, each train occupies a shorter section of track making it possible to run more trains.

On the Blue Line, specifically, the CTA could expand the yard at Forest Park to be able to store more trains for more service on the O'Hare branch. The CTA is only able to maintain its service on the O'Hare branch at current levels by turning around some southbound trains at UIC/Halsted to go back north. The study says having to do this is probably also a capacity limitation but it's the only way to run as many trains on the Blue Line the CTA runs today.

To deal with the lack of electricity to run more trains between Harlem and Grand, the study recommends looking at how power is currently distributed.

The study acknowledges that articulated train cars (also called open gangways, or walk-through) could increase passenger capacity. This is something we've advocated before, as it's used around the world to hold more people and redistribute them across all cars. However, the study says that only the "married" two-car sets should be articulated. Doing this would hold a handful of new passengers, but still have some of the benefits of allowing people to move to a slightly less crowded section of the two cars. The CTA could also extend all platforms to accommodate 10-car trains.

Finally, the study suggests targeting new housing and mixed-use developments along portions of many of the 'L' lines that aren't approaching current capacity. The Orange Line, for example, has suburban-style development patterns surrounding many stations, and has available capacity for more riders. Adding more jobs near Midway airport could also use the available capacity on the reverse commute (headed away from downtown in the morning, and towards downtown in the evening).

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