Birmingham has begun a five-month project to revise 20th Street North between Morris Avenue and Linn Park, which will include staggered closures of 20th St North.
Currently, the northbound lane of 20th St N is closed from 3rd Ave N to Linn Park. This is Phase 1, which is expected to last until early December. When the northbound lane is opened, Phase 2 will begin, which will close the Southbound lane for the same blocks (Linn Park to 3rd Ave N). Thereafter, construction will move to the section of 20th St N between Morris Ave and 3rd Ave N.
More info on these and future planned closures of 20th St North (the main north-south thoroughfare in downtown Birmingham) can be found here. http://revbirmingham.org/20thstreet/
This same project has reduced the lanes of 2nd through 6th Ave North to one lane-only at 20th Street N, causing significant traffic backups at busy times.