alley east of 1st St NW, north of U St NW: heavy traffic congestion yesterday afternoon

From a resident on the unit block of U Street NW - near the alley just east of 1st Street NW, which has become the substitute 1st Street NW:
               
Please see the attached photo. I took this today at about 2:30-3 pm. No one was moving in this instance and things got pretty heated. People got out of their cars and were shouting at each other. That's five cars!
  
We need a solution to the problem and fast!