(CBS) — Problems with switches at one of the busiest rail junctions on the CTA’s rapid transit system made a mess out of the homebound commute Friday evening and could mean delays until at least Saturday afternoon on lines that use the Loop L tracks.

The problems began at about 4:30 p.m. Friday above Van Buren Street and Wabash Avenue, the junction that CTA calls Tower 12.  The inability to throw switches made it impossible for Pink Line and Purple Express trains to use their regular routes; this caused delays to both those lines and the Green, Orange and Brown lines, which share the Loop tracks.

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Pink Line trains were immediately rerouted so that, after making the inbound stop at Clinton, the next stop was Washington/Wells.  Pink Line trains essentially are going around the Loop in the reverse order of their normal routing, and are using the other track — the Outer Loop track.

Purple Express trains Friday evening used the same routing at first, but soon were cut back so that trains operated only between the Linden/Wilmette terminal and Belmont.

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At 6 p.m., a decision was made to cancel Purple Express trains for the balance of the evening, although CTA spokesman Brian Steele said the last scheduled Purple Express train operated, behind schedule.

The Purple Express does not run on weekends.

The delays were so pervasive that, for much of the rush hour, the CTA was urging riders to use express buses that connect at points further north and south of the Loop ‘L’ lines to minimize delays.

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The Pink Line reroute will continue until the repairs are made.  Steele said that could take most of the day Saturday.