SAN DIEGO (NEWS 8/CNS) - Construction crews will begin Monday to build a trolley underpass at La Jolla Colony Drive, according to the San Diego Association of Governments.

Crews plan to re-stripe the street to shift traffic over to the northbound lanes during the first phase of the underpass' construction. During work hours, traffic will be restricted to one lane in each direction.

While this week's work will only last through Thursday, the full underpass will take months to complete. Construction of the entire underpass is complex, according to SANDAG, so work is expected to continue throughout the rest of the year.

The underpass is being constructed as part of the $2.17 billion Mid- Coast Trolley Blue Line Extension, which includes a planned 11-mile extension of trolley service by the Metropolitan Transit System from Santa Fe Depot in downtown San Diego to University City.

The extension will add trolley stops in Mission Bay Park, UC San Diego and Westfield UTC. SANDAG is receiving $1.04 billion in funding from the Federal Transit Administration to complete the project.

The extension and related projects are intended to reduce traffic congestion as the county's population increases. Construction on the extension began in 2016 and is scheduled to be completed in 2021.