Double white lines equal dollar signs for the Washington State Dept. of Transportation. And they—hopefully—mean quicker commutes for drivers east of Seattle.

WSDOT has started installing an additional 300,000 ft of double white lines across a 17-mile stretch of Interstate 405 in the Bellevue area to change the way drivers use I-405 and its two HOV lanes.

Currently, carpoolers now have near unlimited access to the HOV lane, allowed to enter and exit at any point. The new double white lines between Bellevue and Lynwood will create a buffer between the new express toll lanes on the far left side of the road and the regular lanes. Once installed, the double white lines designate that drivers must stay in those lanes, entering and existing the express section only at access points marked by a dashed white line.

Tolling on the pay-for-express lanes starts Sept. 27.

To make it all work, expect more than some extra white lines. Electronic signs post the toll rate based on destination and automatically adjust prices depending on traffic congestion. As more vehicles enter or exit the lanes at the designated access points, the dynamic toll rates adjust so that traffic moves at least 45 miles per hour in the toll lane.

This is the traffic version of supply and demand.

With two express lanes moving in each direction most of the route, HOV drivers can still travel in one lane, with the express toll lane on the far outside. As part of the change, though, WSDOT has upped the HOV requirements to three people per car during peak travel times and requires a registered account to use the express toll lane for free.

We’ll wait and see if this is one toll that proves popular with Washington drivers.

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He writes for Popular MechanicsSports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.