Project "Modernization and Extension of the W-Z Route" began in March 2013 and was ordered by the City of Łódź. Mosty Łódź designed and built the WZ 3 carriageway and implemented carriages WZ 4 to 7.

The following were done in the first constructed section of the route: in the city centre, a new road tunnel with a length of 249 m, with lifts, and the “Piotrkowska Centrum” interchange centre. The modernization also made it possible to provide a tram route between the Retkinia and Olechów districts.

As many as 13.2 km of tram line were modernised as part of the project. The route was opened in October 2015.

Project challenge: Modernization of the W-Z route was one of the largest investments in the Łódź infrastructure in recent years, accompanied by much controversy. Innovative interchange centre with a shelter at Al. Mickiewicza, between ul. Piotrkowska and Al. Kościuszki, called the "Unicorn Stable" by the residents, is today one of the most recognisable buildings in Łódź.