CHICAGO (CBS) — CTA’s Purple Line has seemingly become one big slow zone.

It’s about to become a construction zone, as the transit agency tries to do something about it, WBBM Newsradio’s Bob Roberts reports.

The city of Evanston said Thursday that it is pleased, and that the track work will be the most comprehensive on the line since 1976.

The focus will be replacing rotted ties that are supposed to hold the tracks in place. Bad track means slow speeds. Replacing the ties should restore the trains to full speed until the comprehensive Purple and North Red Line renovation is done.

The work will begin from south to north beginning next month, and work its way to Linden/Wilmette by November.

Residents along the line may be in for some sleepless nights. Work will take place from 9 p.m. until 4 a.m. Sunday through Thursday nights, and between 7 a.m. and 7 p.m. on weekends.

The CTA’s latest slow zone map shows that 38 percent of the Purple Line is considered a slow zone. In addition to replacing rotted ties, the rest of the track structure, including rails, tie plates and ballast, could be replaced where conditions warrant.

CTA will distribute fliers to local residents advising them when construction is beginning in their area.

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