Metro plans to set aside nearly $70 million over the next six years to expand two of its busiest stations to ease packed platforms and dangerous crowds.

Tens of thousands of riders trek through Union Station and Gallery Place-Chinatown every weekday -- an average of 33,250 and 26,587, respectively -- and officials are worried the crowds that surrounded an elderly couple who fell into the tracks in April 2011 at Gallery Place could get even more dangerous in the future.

"The confused layout of the [Gallery Place] station causes a lot of risk. You have people coming up, down, making turns, others running because they're trying to catch the back end of a six-car train," said Metro board member Mort Downey. "[The expansions] certainly will be passenger convenience, but it's also a safety issue."

Red, Yellow and Green passengers transfer at Gallery Place, the Metro system's fourth-busiest station, and Amtrak, MARC, VRE and bus riders hop on the Metro at the Red Line's Union Station, Metro's busiest station. Agency planners expect Gallery Place to get even more crowded with the opening of mega-development CityCenterDC later this year.

The upgrades could include larger mezzanines, adding escalators and elevators and widening Gallery Place's tight corner on the east end of the Shady Grove platform, said Metro spokesman Dan Stessel. Metro planners' 2011 study of Union Station also suggested relocating the station's First Street entrance, adding more faregates and moving the elevator.

The $70 million to expand the stations is included in Metro's proposed six-year plan, which a Metro committee has approved, but most of the money won't come through until 2018 and 2019. Metro officials said that's because more planning is needed before construction can start.

"It's not something you can rush into," Downey said, adding that Metro will have to work with Amtrak and others to make the changes to historic Union Station. Historic building concerns also could hamper efforts at Gallery Place -- Metro planners noted that the underground piles supporting the National Portrait Gallery limited the original width of the Red Line platforms there.