After the Alaskan Way Viaduct closes to traffic forever on January 11, it’s time for the Washington State Department of Transportation (WSDOT) to direct State Route 99 away from the elevated freeway and through the brand-new tunnel. That whole process will take about three weeks, and requires completely closing SR 99 through downtown. In a new video—embedded above—WSDOT details what work will be done during that timeframe.

If you’ve been in a car on 99 in the past few years, you’ve probably noticed some weird-feeling, curvy pathways. That’s because those are temporary detours installed during tunnel construction. Much of the work is removing those detours.

On the north end, cars have been driving right past the tunnel entrance for a while. Realignment there means removing a temporary wall, allowing traffic to flow into the tunnel.

The south end requires a lot of road-untangling. Early in construction, ramps into the tunnel were constructed, then buried. Crews need to demolished the bow-shaped detour into the tunnel near the stadium, build new roads to the new ramps, then unearth the ramps themselves.

WSDOT also needs to make connections to the northbound offramp to downtown at the south end of the tunnel, a bridge that was built about a year and a half ago. That ramp could open up to two weeks after the rest of the tunnel.

When all the connections are complete, the two-mile, eventually tolled tunnel will carry cars from around the stadium district to Aurora Avenue North near Seattle Center. The tunnel was initially projected to open in December 2015, but after a two-year delay halted the drill from completing work until April 2017, the projected opening date was moved to early 2019.

When the tunnel opens, the viaduct is slated for demolition—but a weekend-long tunnel-opening party offers a few chances to say goodbye, with a bike ride, an 8K run, and scheduled tours.