The effort to improve efficiency and capacity at Union Station has taken another step forward, as Metro begins preparing an environmental impact report for a long-planned series of upgrades to the historic rail terminal.

Link Union Station, formerly known as the Southern California Interconnector Project, would allow Amtrak and Metrolink trains to pass directly through the station by creating as many as ten new tracks running south across the US-101 freeway trench, as well as a new loop track for operational flexibility. This upgrade, previously budgeted at $350 million, would increase Union Station's capacity by as much as 50% and shave train idling times by up to 25 minutes. Currently, the station's stub-end layout forces all trains to arrive and depart through the five-track throat located north of the railyard.

Although the notion of building run-through tracks has been suggested for decades - most recently in 2006 - Metro's expanding rail network has made Union Station's built-in limitations more apparent. According to documents from Metro, the station is already approaching its operational capacity, with an estimated 110,000 riders passing through on each weekday. With extensions in the works for multiple transit lines that serve Union Station, that number is expected to swell to 200,000 by the year 2040.

Accordingly, the rebranded Link US effort is larger in scope than earlier attempts.

Most notably, the project now includes an expansion of Union Station's passenger concourse, as envisioned in Metro's 2014 master plan for the property. The larger concourse would span up to 600,000 square feet and offer new waiting areas, improved passenger circulation and retail amenities for tourists and commuters.

Additionally, plans call for increasing the elevation of both the throat and the rail yard to allow for longer passenger platforms and canopies. The lengthened platforms are critical for accommodating California High-Speed Rail, which could have up to four dedicated tracks in the Union Station rail yard.

The project will require coordination between Metro and numerous other agencies, including the Federal Railroard Administration, the Southern California Regional Rail Authority, Caltrans, the City of Los Angeles and Amtrak.

A final environmental impact report and a record of decision is expected by Winter 2017.