CHICAGO -- Beginning Sunday, enhancements will be made to select CTA bus routes and four-track operations will resume at two North Side train stations.

Permanent service enhancements will be made on the Ashland (No. 9), Laramie (No. 57), Austin (No. 91), Stockton/Michigan Express (No. 143) and North Harlem (No. 90N) buses. All buses will provide additional service expect for the North Harlem bus, which will run less frequently.

The CTA will also have experimental bus service enhancements on King Drive (No. 3), Roosevelt (No. 12), 16th/18th (No. 18), Cermak (No. 21), 35th Street (No. 35), West Loop/South Loop (No. 129), Inner Drive/Michigan Express (No. 146) and Central/Ridge (No. 201) buses.

All the experimental service enhancements involve changing bus routes and rerouting buses to eliminate turns.

With the completion of three-track operations at the Belmont and Fullerton stations, Red, Brown and Purple Express trains have resumed normal operation on all four tracks.

The extra track allows Red Line trains to operate eight minutes faster, Brown Line trains to operate seven minutes faster and Purple Express trains to operate five minutes faster.

Additionally, Purple Line Express trains will return to traveling clockwise beginning Monday.