MERCER ISLAND, Wash. -- Mercer Island city leaders have voted to sue the Washington Department of Transportation and Sound Transit the carpool ramp access on I-90.

Residents driving alone have been allowed to use them, in part because I-90 is the only way on or off the island. But soon those express lanes will be turned into light rail lines, with construction starting the summer, taking that route away.

"It's beyond anything that's been considered in the past," said Mayor Bruce Bassett, "It impacts us in ways that have not been studied and are more severe than we expected."

Council members say they're concerned the loss of the access ramps from Island Crest Way, a four-lane arterial, would result in congestion around the Town Center. The state informed the city earlier this month it would no longer grant solo drivers special access to the new high-occupancy vehicle lanes while those HOV lanes are closed.

The suit aims to jump-start a negotiation.

Mercer Island also voted to seek a moratorium on construction of the light rail and a Mercer Island Sound Transit station, scheduled to be built over the new few years, while the case is in litigation.