For more than a decade, planners and politicians have talked about Metro’s new Silver Line and all the possibilities it might bring.

Now, with the first phase of the nearly $6 billion rail line scheduled to open in just nine months, Metro officials are making perhaps their toughest sales pitch: to riders.

Last week, about 400 people attended three open houses Metro held across the region to explain how the sixth line in the transit system will operate with existing lines as well as to get feedback.

“Most riders are going to do the same thing they’ve always done in their commute, but it’s a big change to have a new line open,” said Jim Hughes, who’s leading the operations plans for the new Silver Line for Metro. “It’s new and different.”

At an open house Saturday, riders strolled through a conference room at the Sheraton Crystal City to look at Metro maps and posters featuring estimated travel times. The Silver Line will include five stations and 11 miles of new rail from East Falls Church to Wiehle Avenue. It is expected to add 17,000 new riders to the system on an average weekday and to open to customers by the end of the year.

The first phase of the Silver Line will carry passengers through Tysons Corner to Reston.

“It will be a nice option, but it also could possibly be more chaos as people get used to it,” Krystal Ramirez, 24, of Rosslyn said as she studied a map showing how the line will go through Tysons Corner.

At the recent open house forums, some riders have said they’re concerned about the lack of parking at the Tysons Corner stations where planners want to create more of a walkable downtown area around the subway.

Some of the roughly 8,000 riders who commute between the southern portion of the Blue Line in Northern Virginia and points west are worried that the new line leaves them fewer Blue Line trains.

With the Silver Line, that means more trains have to use the Rosslyn tunnel to cross the Potomac River. But the tunnel is already at its capacity of 26 trains an hour, so some trains that now run on the Blue Line will have to switch over to the Yellow Line to make way for Silver Line trains.

The number of Blue Line trains affects riders such as Melissa Nasrah, 39, of Crystal City.

She rides daily to her job as a lawyer at the Treasury Department, getting off at McPherson Square. Since Metro introduced its Rush Plus service this summer, where it has fewer Blue Line trains, she said her wait in the evenings can be 15 minutes — longer than the 14-minute train ride.

“I know this is the long-promised line that’s now coming,” she said of the Silver Line. “But it feels like the Blue Line is taking a lot of hits.”

Metro planners advised her to get on the first Yellow Line train she sees and switch at L’Enfant Plaza.

“I guess I’ll have to try that,” she said. Or, in nicer weather, she simply runs from her office to home. Total commute: 38 minutes.