That may be a CalTrans issue, since they are doing cleaning/maintenance in the Posey Tube at night. It could also be traffic backing up from Alameda, from people going to the new shopping center near College of Alameda.

To add: the primary issue is with the traffic moving down 5th to enter the tube and the demand-triggered light for traffic crossing 5th to continue on Washington. If the light on 5th at Broadway is green (so cars can enter the tube), the light on 5th at Washington must also be green. Every time. I can't say how many times I've seen the Broadway crossing lights green with no cars able to go through to Alameda because suddenly a car on Washington triggered the light to cross and now everyone is backed up.. This situation not only prevents cars from accessing Alameda efficiently (thereby causing a huge traffic back up on fifth street) but it also stops traffic on Broadway while cars sit for a green light nobody can use polluting our community. It also leads to people blocking the Washington intersection because they are sick of sitting in traffic to get home in Alameda. The most frustrating thing is this seems to be relatively preventable with a simple light adjustment.