Traffic Lab is a Seattle Times project that digs into the region’s transportation issues to explore the policies and politics that determine how we get around and how billions of dollars in public money are spent.

Bus riders in many corners of King County will enjoy more frequent service, and a few new routes will feed light rail stations, when seasonal transit shake-ups hit the streets Saturday.

King County Metro Transit is adding 3,000 trips per week, most funded by county taxpayers, plus money from a Seattle sales tax for supplemental city service.

Metro’s new Route 77 bus from Bitter Lake goes to the nearly finished Pinehurst light rail station, along the Northeast 130th/125th street corridor that’s being rebuilt to favor transit and bikes over fast driving. The station along I-5 lacks a parking garage — and still has minimal housing nearby — so Sound Transit will count on crosstown buses between Bitter Lake and Lake City to deliver people to the trains.

These buses, typically arriving every 15 minutes, continue on Lake City Way Northeast, to Roosevelt Station, U District Station and Seattle Children’s hospital.

Weekday service will increase along Route 8 on Denny Way, providing trips every 12 to 15 minutes, where an eastbound general traffic lane was just converted to a red bus-only lane. Buses after 9:30 p.m. will still be 30 minutes apart.

South King County residents will find more bus connections to light rail stations, such as the new Route 164 from Kent’s East Hill to Kent Des Moines Station, and revised routes 182, 183 and 187 to Federal Way Downtown Station. The Metro Flex on-demand vans will expand to Auburn and Federal Way.

Community Transit announced more weekend trips on popular routes, such as the Swift Blue Line from Everett and Highway 99 to Shoreline North/185th Station; 201/202 between Smokey Point and Lynnwood City Center Station; and 908 from Snohomish Park & Ride to Bellevue.

A new Cathcart Park & Ride is opening along Highway 9 in the growing Silver Firs area, while a new stop will be added on West Casino Road in South Everett, to serve apartment complexes.

Sound Transit will retire Route 550 from Bellevue to Seattle over I-90, along with 554 from Issaquah to Seattle via I-90, now that light rail’s 2 Line crosses Lake Washington. Route 556 from Issaquah to the University District will be shortened to end in downtown Bellevue, where commuters are expected to catch the 2 Line to the university.

The agency is scrapping Route 515, which was meant to be temporary, between Lynnwood City Center Station and downtown Seattle, as light rail service from Lynnwood has been firmly established since August 2024.

Many other routes are changing. For details, watch for signs at bus stops, and visit www.soundtransit.org, www.kingcounty.gov/en/dept/metro, or www.communitytransit.org.