Engineering and construction firm Fluor and its joint venture partner Walsh Construction Company have begun the Red and Purple Line Modernisation programme of Chicago Transit Authority (CTA).

The phase one of the Red and Purple Line Modernisation is the largest project undertaken by the CTA.

The $2.1bn project is jointly funded by federal and local governments.

The JV will be responsible for building a new bypass bridge to reduce congestion on the 100-year-old rail line in the Lakeview neighbourhood, where three rail lines intersect.

The bypass will increase the train speed and CTA’s train capacity during the rush period.

The companies will also rebuild around two miles of tracks and replace four CTA stations. The project also involves upgrading the signal system.

The four new stations will feature elevators, improved lighting and security, windscreens, wider platforms, longer canopies and real-time information boards.

Fluor Infrastructure & Power group president Terry Towle said: “We are pleased to be a partner to CTA in modernising its 100-year-old rail system.

“This modernisation project will create capacity for decades to come, which will allow CTA to provide more reliable service on modern infrastructure.”

The project involves multiple steps to mitigate its impact on environment, residents, businesses and patrons, pedestrians, as well as bicycle and car traffic.

The construction is scheduled to be completed by 2025.