Tolling on one of the state's busiest bridges is set to begin Thursday, but state transportation officials are expecting traffic on the route to be much lighter than usual.

Washington DOT says roughly 120,000 drivers use the bridge on a normal workday, but WSDOT expects 40,000 drivers to seek another route, which will affect traffic the Interstate 90 bridge and Interstates 5 and 405.

Traffic is usually down about 20 percent because of the holiday week -- and that's before thousands of motorists choose to find another, toll-free route, such as the toll-free Interstate 90 bridge or Highway 522. The real test will come Tuesday, when more people return to work and the University of Washington begins winter classes.

The Associated Press reports studies suggest that 20% of the usual number of daily vehicle trips will switch to I-90, while 15% will take transit, different roads, change their travel time or not travel at all.

At the beginning of this week, just one-fifth of bridge users had already put the Good to Go transponders -- which work like debit cards -- on their windshields.

About 140,000 new accounts have been created since February, mainly for Highway 520. Well over a quarter-million passes have been sold overall for 520, the Narrows Bridge and Highway 167 high-occupancy or toll (HOT) lanes combined.

Tolls will vary by time of day. Peak-time rates for a five-axle truck vary from $8.75 for vehicles with a Good-to-Go transponder, to $12.50 for trucks billed by mail. There are no tolls overnight (11:00 PM to 5:00 AM).

Tolling was originally slated to start this past spring, but glitches with the electronic system set up by Texas-based ETC Corporation delayed the start.

More info:

Good to Go Toll Schedule