Bolstered by billions of dollars in new funding, Metro is moving forward with plans for a two-pronged extension of the Gold Line's Eastside branch.

Measure M, the half-cent sales tax that was passed by more than 70 percent of Los Angeles County voters in November, allocates funding for an extension of the light rail line from its current terminus at Atlantic Station towards the cities of El Monte and Whittier.

According to a post on the Source, the first leg of the extension would be constructed between 2035 and 2057, although the Metro Board has yet to select which route will come first. However, Metro is actively exploring strategies to accelerate construction the project, as well as several Measure M rail and bus lines.

A 2014 environmental impact report for the Eastside extension had pondered two distinct routes, one of which would roughly parallel the SR-60 freeway, and another that would meander along city streets toward Whittier. A follow-up study has retained the same end destinations, but envisions several different pathways.

For the SR-60 alignment, Metro is now considering moving a portion of the aerial tracks to the north side of the freeway in order to avoid crossing through a former landfill in Monterey Park.

For the Whittier branch, Metro has now discarded plans for an aerial alignment down Garfield Avenue, citing complaints that the proposed structures would loom over an adjacent bedroom community. Of the various new alignments under consideration, a potential underground route beneath Atlantic Boulevard is cited as promising. This alignment would run through the City of Commerce, with a stop at the Citadel Outlets.

Though key for developing a coalition in support of Measure M, the two-pronged approach poses challenges from an operational standpoint. The current Eastside Gold Line will eventually be merged with the Expo Line following the completion of the Regional Connector subway, and it is unclear how further extensions will affect service patterns.

Additionally, having two branches Splitting the Gold Line at Atlantic means that it becomes more difficult to run five-minute headways towards both South El Monte and Whittier. According to the Source, Metro is studying a junction that would allow trains to run between South El Monte, Atlantic and Whittier, thus maintaining more frequent service.

Metro is offering more information on the project through a series of community meetings over the next two weeks. The Metro Board is scheduled to consider the findings of the most recent study in Spring, and the environmental process is to be reinitiated in either the Summer of Fall of 2017.