Virginia's Metro commuters could get some relief on their crowded train rides starting next summer, as the transit agency is planning to reroute some Blue Line trains across the Yellow Line bridge.

But those riders can expect major confusion as to which train goes where: The straightforward Blue lines on the Metro map will be tangled up with the Orange, Yellow and Green. Metro officials have been working through the plan for years, trying to find a way to clearly communicate the switch.

"What we heard from everybody is: This is confusing," said Jim Hughes, a Metro planner who is leading the proposal.

The change would entail rerouting a third of the Blue Line trains along the Yellow Line bridge crossing the Potomac River and up to Greenbelt, along the current Green Line.

Three Orange Line trains per hour would be added, running from the Orange Line's West Falls Church stop to Largo, the Blue Line terminus, instead of the Orange Line's New Carrollton.

Metro officials also are looking to add supplemental bus service.

The reason for the change is that there are just two ways for Metrorail to cross the Potomac River into the District from Virginia. The bottleneck occurs at Rosslyn, the last stop in Virginia along the Blue and Orange lines before crossing into the District. It currently carries the system's maximum of one train every 135 seconds, with 16 Orange Line and 10 Blue Line trains per hour at the height of the commute, according to Metro. If a train has a problem on what riders call the "Orange Crush," a domino effect of delays occurs.

More pressure will come on that station when the Dulles Rail extension begins in late 2013.

Ridership patterns are shifting already, as the southern portion of the Blue and Yellow lines has shown faster ridership growth than the overall system.

"The demand is shifting out there," Hughes said. "We want to be ahead of what's coming with Dulles."

The change would help an estimated 14,800 riders, Hughes said, but would "slightly inconvenience" about 12,000 others.

The key, though, is how to communicate the change to riders, using signs and maps so visitors know how to get around. Metro is planning to work out a plan in the coming months before changing the trains next summer.

Yet an Orange Line change proposed years ago became so confusing that Metro abandoned it, noted Metro board member Peter Benjamin.

Fellow board member Jim Graham suggested picking an entirely new color for the new service. "Pink?" he said Thursday. "We've got many colors left in the rainbow."