A short walk-bike tunnel will be built in the Factoria section of Bellevue this weekend, and it will temporarily close both the northbound and southbound Interstate 405 offramps that lead to eastbound Interstate 90.

The closure will go from 10:30 p.m. Friday until 5 a.m. Monday, the Bellevue Department of Transportation (DOT) announced. The tunnel, below those two freeway ramps, will give people a refuge from hectic shopping-center traffic, and fill a gap in the 100-mile Mountains to Sound Greenway Trail.

Bellevue DOT didn’t map a detour route, but it says the ramps from both Bellevue Way Southeast and Eastgate at 150th Avenue Southeast will remain open. For bicyclists, the I-90 trail will stay open, but riders on the I-405 trail this weekend must detour around a closed area near Factoria mall.

Travelers on Factoria Boulevard Southeast can already see a new trail bridge being built above that road. The Factoria section near I-405 costs $17.7 million, mostly state-funded, to be done by late 2020. Future trail projects will continue east from 132nd Avenue Southeast to Lakemont Boulevard Southeast, next to Lake Sammamish.