Tens of thousands of Metro riders will face longer waits and more crowded trains with the arrival of Metro's new Silver Line, expected late this year -- but hundreds of thousands of other riders will see shorter waits and fewer crowds, the transit agency predicts.

Metro expects 82,556 trips taken on its system daily will require a longer wait for a train and more stuffed railcars, according to a new analysis due to be presented to Metro's board of directors on Thursday.

That's because the new Silver Line, which will extend Metro to Reston through Tysons Corner, will take up scarce space in the Rosslyn tunnel, which carries Orange and Blue trains.

Blue Line riders will wait 12 minutes for the next train, even during rush hour, and riders coming from the west end of the Orange Line -- at the Vienna, Dunn Loring and West Falls Church stations -- will see trains come every six minutes during rush hour.

Meanwhile, nearly 400,000 people will benefit from the Silver Line changes, Metro staff concluded.

"By about a 5-to-1 margin, people benefit from the changes," Metro spokesman Dan Stessel said, pointing out than an earlier plan had Blue Line trains coming every 14 minutes, instead of 12.

But Riders' Advisory Council Chairman Ben Ball said he thinks Metro needs to do more to help Blue Line riders.

"Metro needs to start thinking about what it can do for those riders, whether it be some sort of fare adjustment, some sort of alternative bus service," Ball said. "These people are going to be affected by this for a long time."

Metro also found in a survey that just half of its riders know the Silver Line is coming -- "lower than expected regional awareness," it said in the report. More Fairfax County residents knew about the new line, about 75 percent.

But Metro's survey of nearly 10,000 people found that many say they will use the new Silver Line, with 64 percent of all Metro riders saying they would use it, and 79 percent of people who work in Fairfax County saying they would.