From the CTA:

Due to signal system work, Blue Line (O’Hare branch) trains will be temporarily rerouted as follows:

• 11 p.m., Friday, September 28 until 11 a.m., Saturday, September 29, 2007

Southbound Blue Line trains will operate on the northbound track in various sections between the Addison and Logan Square (accessible) stations. Please board southbound trains on the northbound platform.

• 10 p.m., Saturday, September 29 until 10 a.m., Sunday, September 30, 2007

Northbound Blue Line trains will operate on the southbound track in various sections between the Logan Square (accessible) and Addison stations. Please board northbound trains on the southbound platform.

Trains may be delayed. Please allow extra travel time.