Chicago Mayor Rahm Emanuel and the Chicago Transit Authority (CTA) recently announced plans to begin renovations of the Red and Purple Lines in 2017. The CTA hopes to begin an extension of the Red Line further south after these renovations are completed.

The agency plans to replace parts of tracks on the Red and Purple Lines as well as build at least five miles of new track as an extension of the Red Line. The Red Line currently runs from 95th Street to the Uptown neighborhood, remaining parallel for much of its length to the Purple Line, which runs from the Loop to Wilmette, a suburb north of Evanston.

In a $1.7 billion project, what CTA President Forrest Claypool described in a CTA press release as “outdated infrastructure” will be replaced with “modern, efficient rail.” Most Red and Purple Line tracks are nearly 100 years old, and a significant amount of time and money is currently spent on repairs, hindering service greatly, according to the press release. These tracks will be replaced and five stations originally built between 1908 and 1923—Wilson, Lawrence, Argyle, Berwyn, and Bryn Mawr—will be completely rebuilt, with new elevators to improve accessibility.

According to the press release, in a spot north of the Belmont station in the Lakeview neighborhood where the Red, Purple, and Brown Lines all intersect, delays of up to three minutes often occur because trains on the Red and Purple Lines must wait for Brown Line trains to cross. In order to remedy this, a bypass will be built, allowing the Brown Line to cross over the Red and Purple Lines. According to an article in Chicagoist, the CTA will have to buy 16 buildings between Belmont Avenue and Addison Street in order for this bypass to be built, which is included in the $1.7 billion cost of the first phase of the project.

The second phase is a $2.3 billion endeavor in which the Red Line will be extended from 95th Street through the Roseland community south to 130th Street, a low-income area that largely depends on public transit but lacks the infrastructure that is available in other areas. The project is expected to shorten the commute from 130th Street to downtown by 20 minutes, allowing better access to education and jobs downtown, according to the CTA press release.