If you see more police officers directing traffic at intersections this week, here’s why.

SEATTLE — Additional Seattle police officers will be stationed at intersections in downtown Seattle and SODO this week to help keep traffic flowing during a three-week State Route 99 closure.

The Alaskan Way Viaduct closed for good Friday night, and it will be another three weeks until the new tunnel under downtown Seattle opens. During that time, which is called “the period of maximum constraint,” traffic is expected to get worse.

Starting Monday, officers will help direct traffic, keep bus lanes and intersections clear, and keep cars and pedestrians moving.

They will be stationed at the 14 busiest intersections during the peak morning and evening commute times, which are 6-10 a.m. and 3-7 p.m.

Those intersections are:

Downtown Seattle – Denny Way and Aurora Avenue North, Fifth Avenue and Wall Street, Sixth Avenue and Wall Street, Denny Way and Battery Street, Fifth Avenue and Olive Way, Third Avenue and Stewart Street, Fifth Avenue and Stewart Street, First Avenue North and Denny Way, and Queen Anne Avenue North and Denny Way.

SODO – First Avenue South and South Atlantic Street, South Royal Brougham Way and Fourth Avenue South, Fifth Avenue South and Seattle Boulevard South, Sixth Avenue South and South Royal Brougham Way, South Spokane Street and Fourth Avenue South.

Seattle Police Assistant Chief Steve Hirjak said Thursday the effort was about working with the community during the closure, although he wasn’t taking tickets off the table. For example, traveling in or blocking a bus-only lane could get you a $158 ticket.

To ease congestion, commuters are encouraged to work from home, work flexible hours, try a vanpool or carpool, or take public transit. If you have to drive downtown, drivers are urged to not “block the box” or block an intersection or crosswalk, because it contributes to gridlock. If you don’t think you can make it through a green light or know you will have to stop in the intersection, stay back.

Seattle Department of Transportation Director of Downtown Mobility Heather Marx said drivers should plan on adding an extra 30 minutes to their commute times during the closure. Some King County Metro buses could see 30-60 minutes of added travel time on some routes, according to King County Metro Managing Director Bill Bryant.