Heads up for late-night drivers, especially if you’re going to a holiday party someplace to the south: Northbound I-5, starting just south of West Seattle, will have a six-mile shutdown overnight tomorrow (Saturday night into Sunday), and an even-more-extensive one next Saturday, for sign installation. Read on for the full details from WSDOT:

Don’t let the cold weather and holiday lights fool you, WSDOT crews are still hard at work in December. For the next two Saturday nights crews will close six miles of northbound Interstate 5 through south Seattle to install 15 overhead sign bridges.

The new sign bridges will hold overhead electronic signs alerting drivers to reduce their speed or change lanes when there are collisions or backups on the road. The new signs are the latest smarter highway technology aimed at increasing safety and reducing collisions. The $23.8 million project is funded by the Alaskan Way Viaduct program to help keep traffic moving during viaduct demolition and construction.

“Getting these sign bridges up is the first major milestone in making northbound I-5 a safer and smarter highway,” said Craig Stone, WSDOT Toll Division Director. “We’ll spend the rest of the winter and spring installing the high-tech signs before activating them next summer.”

Crews will close all lanes of northbound I-5 from 11:30 p.m. Saturday, Dec. 5, to 8 a.m. Sunday, Dec. 6, between Boeing Access Road and Spokane Street. I-5 on-ramps in the area will start closing as early as 9 p.m. Crews will again close all lanes of northbound I-5 from 11:30 p.m. Dec. 12 to 8 a.m. Dec. 13 between Boeing Access Road and I-90.

The following ramps will be closed from 9 p.m. Saturday, Dec. 5, to 8 a.m. Sunday, Dec. 6:

o Boeing Access Road and Martin Luther King Jr. Way S. to northbound I-5
o Swift Avenue S./S. Graham Street to northbound I-5
o Corson Avenue/S. Michigan Street to northbound I-5

A signed detour will direct drivers to exit at Martin Luther King Way (exit 157) to Airport Way and back onto I-5 via Edgar Martinez Way/SR 519. Drivers should consider taking alternate routes like I-405 or SR 99 to avoid long delays and backups.