Nearly half a million people are expected to sail on Washington State Ferries in the next few days, WSF officials announced this week, which will most likely mean long waits and some delays for Labor Day weekend travelers.

“More than 400,000 people are projected to ride a ferry over the next five days,” WSF spokesman Ian Sterling said Thursday. “That’s equal to six sellout crowds at CenturyLink Field for a Seahawks game — and part of the reason passengers should allow for extra travel time during the Labor Day weekend.”

That daunting estimate comes in the midst of some of the highest ridership numbers in more than a decade, Sterling said, despite several disruptions this summer for vessel repairs. With the M/Vs Hyak, Salish and Samish currently out of service, the Fauntleroy/Vashon/Southworth route is on a reduced two-boat schedule to balance service needs across the system.

WSF expects many holiday weekend passengers to sail westbound Friday, Sept. 1, and eastbound Monday, Sept. 4, as people return from their Labor Day getaways. There will be additional service Monday on most routes, but passengers should still expect crowds and lines during peak travel times.

“What better way to close out the summer than a scenic ride on a cultural Northwest icon,” WSF Assistant Secretary Amy Scarton said. “But with the added traffic and adjusted schedule on some routes, we encourage all passengers to pack some patience this holiday weekend and prepare for longer wait times.”

It’s been a busy summer for WSF already.

Officials said the ferries carried nearly 5.5 million people from late June to late August this year. More than 25 percent of all passengers took the Seattle/Bainbridge Island route, which recorded 1.4 million customers. The second busiest route was Edmonds/Kingston with about 900,000 people.

Ridership is up 40,660 passengers from the same time period in 2016, WSF officials said.

It’s not just on the water, either that travelers are being encouraged to allot a little extra travel time this weekend.

Washington State Department of Transportation is warning travelers on I-90 of likely “significant congestion Friday and Monday.”

Travelers can use the Washington State Department of Transportation’s traffic volume charts (www.wsdot.wa.gov/congestion/laborday/2017/driver-tips) this holiday weekend to “know before they go” and help time their travel on key routes. In particular, this year, holiday congestion is expected on Interstate 90 near Snoqualmie Pass – especially westbound traffic.

Eastbound travelers, officials said, will experience delays on Friday, Sept. 1, and should consider traveling early in the day or late in the evening.

Westbound travelers should expect major delays Monday, Sept. 4, near the detour. If possible, travelers may want to leave early, officials said, or possibly extend their return trip into Tuesday, Sept. 5.

They also cautioned that the WSDOT I-90 travel charts do not reflect delays due to construction work, but they can still be used as an overall guide to the times when the most congestion is expected.