SEATTLE - Fourth of July travelers and other drivers on westbound I-90 were stuck in backed-up traffic as the holiday weeekend came to a close. WSDOT says the traffic nightmare is only going to get worse during the next two weeks.

Early Monday, crews will begin work on I-90's expansion joints. While they replace the joints, the regular westbound lanes will be closed. Westbound traffic will be moved onto the express lanes but DOT warns traffic will be slow-going.

WSDOT has released this construction timeline for I-90:

Sunday July, 5 from 9:00pm to 5:00am - I-90 bicycle and pedestrian path temporarily closed for construction
Monday July, 6 5:00 am - All Westbound I-90 traffic funneled into the two I-90 express lanes on Mercer Island (Expect Severe delays)
Monday July, 20 - All lanes open in time for the commute

Drivers who rely on I-90 are told to:
-Allow extra travel time during construction.
-Leave early, before 6:00am on weekdays

WSDOT Assistant Regional Administrator Russ East warns the work on I-90 will have a ripple effect on several other freeways and highways "every one of those routes is already congested, today, and so we expect to see heavy congestion throughout our entire transportation system."

Drivers caught in the back-up Sunday were a little frustrated by the slow traffic. Catherine Seneviratne said "it's not the best timing with all the stuff going on." But WSDOT says if they start now, they should be done with the project before Seafair starts.

Many drivers said they were aware of the construction but said they understand the work has to get done. JW Hanberry said "it's better than the expansion joint failing while I'm in mid-span." He plans to take other routes on most of his work days but said at least one day each week he will have to fight the traffic.