NORWALK, Conn. — Connecticut's Department of Transportation and Metro-North Railroad are moving ahead with agreements to eventually replace the 120-year-old swing bridge over the Norwalk River.

DOT and Metro-North recently signed a "partnering letter," agreeing to their shared goals for the project. The letter also spells out schedules of meetings to ensure open communication.

Construction of the new Walk Bridge is not expected to begin until mid-2018. Three advance construction projects must be completed before the aging railroad bridge can be replaced.

The bridge carries four tracks across the river and is considered a key link on the New Haven Line. It carries more than 165 commuter and freight trains daily.

Metro-North is one of the nation's largest commuter railroad systems. It connects New York City, its northern suburbs and Connecticut.