In the last year, a few readers have asked why their Orange Line train turns Brown in the Loop. Here's why:
To accommodate increased ridership, there have been some trains departing from other terminals and changing over at some point to operate as Brown Line trains, according to a CTA spokesperson. This car-train movement from one rail line to another is done due to the rail yard capacity constraints at Kimball. The Kimball rail yard is too small for the number of car-trains needed for service.
Currently, two trains from Howard and one train from Midway are assigned to help supplement Brown Line service during the AM rush period.
From Howard, the trains operate as Purple Line Express to Belmont. At Belmont they become Brown Line trains that serve the Loop and return northbound to Kimball to make a second southbound Brown Line run. After going around the Loop twice as Brown Line trains, the trains then switch to Purple Line Express service after Clark/Lake and operate northbound to Howard.
However, when the the CTA's Crowd Reduction Plan goes into effect next month, two additional trips will be added to Brown Line service. At that time, to streamline operations, all five supplemental AM rush period Brown Line trips will originate from Midway and return to Midway after completing a Brown Line trip to/from Kimball.