Eric Richardson / blogdowntown

Cars follow a Gold Line train along the First Street Viaduct, where westbound traffic lanes were reopened this week at the completion of a four-year widening project.

DOWNTOWN LOS ANGELES — The westbound side of the First Street Viaduct reopened to traffic this week, bringing to a close a four-year project to accomodate the Gold Line's Eastside Extension by widening the bridge, which connects Downtown and Boyle Heights.

A ribbon-cutting for the new lanes with Councilmembers Jan Perry and Jose Huizar will be held atop the bridge on Tuesday, December 20, at 9am.

The rail line opened in November of 2009, but westbound traffic on the 1929 bridge has remained closed as crews completed work to add 26.3 feet to the structure's width. The Gold Line tracks run down the middle of the bridge, hugged by two lanes of traffic in each direction.

To make the extra room, the bridge's historic towers were disconnected from the rest of the structure and stored nearby while the structure for the extra lanes was built.

For the City of Los Angeles, the project represents a major achievement in historic preservation. The new work matches the design of the old, and includes the iconic towers in their appropriate positions. On Friday morning, crews were at work on the original, south face of the span, touching up the structure's coat of paint in preparation for next week's festivities.

The First Street Viaduct is one of the series of classic Los Angeles River bridges designed by city engineer Merrill Butler.