Caltrans is doing ongoing construction on a section of I-80 through the middle of San Francisco, and a portion of eastbound I-80 will be completely closed for 55 hours this weekend, forcing motorists onto surface streets to get to the Bay Bridge.

Expect mass confusion and probably plenty of traffic around SoMa and mid-Market due to this two-day closure of I-80 in San Francisco which starts on Friday, April 17,  at 11 pm, and lasts until Monday at 6 am.

The video below explains how the detours are supposed to work for those traveling through the city and trying to get to the Bay Bridge, and those traveling north on 101 from the Peninsula and attempting to get to the Bay Bridge. In both cases, the section of eastbound 80 that runs between about 15th Street in the Mission to 5th Street in SoMa will be closed, and drivers will have to go around and get to the bridge either via the 5th Street onramp, or the Essex Street onramp.

If you want to get really turned around, check out this map of the situation from Caltrans, in which North is left, and East is up.

Caltrans is encouraging people to use public transit to get across the Bay during this closure, which again will start late Friday and go all the way until Monday morning.

Why is this happening? Well, Caltrans started a two-year project in January to to rehabilitate the Central/Bayshore freeway viaducts — so this isn't the last disruptive closure you can expect. The work this weekend includes "essential structural and bridge deck rehabilitation that will enhance safety and extend its life."

You can expect, at best, there will be some significant traffic backups on Folsom Street and near the Embarcadero/First Street getting to the Essex Street or First Street onramps, and a lot of traffic on Bryant Street as well getting to the 5th and Bryant onramp.