By John Dodge

CHICAGO (CBS) — Starting as early as 2017, the CTA plans to rebuild four stations and begin to replace track and elevated structures on the north part of the Red Line.

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The cost of that project is $1.1 billion.

The stations, part of a plan to rebuild the north Red Line and Purple Line, are at Lawrence, Argyle, Berwyn and Bryn Mawr. All four stations will be equipped with elevators.

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While funding still needs to be lined up, the project will eliminate the kind of slow zones that also plagued the southern portion of the Red Line before it was rebuilt last year.

The overall Red and Purple project calls for replacing stations and upgrading track from north of the Belmont station to the Linden station in Wilmette.

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The total cost is estimated to cost between $2 billion and $4 billion.