I'd actually be surprised if adding bike lanes to these streets didn't improve traffic flow. The thing is, they really aren't wide enough for two lanes of traffic, more like 1.75 lanes of traffic. Two cars can't drive parallel to each other safely throughout, especially once you add in the random parked delivery vehicles, and so a lot of the congestion is actually caused by cars weaving in and out of a one-lane and two-lane configuration, and having to drive quite slowly when it is in a two-lane configuration because there's barely any room between the cars.
The point is, I'd bet one clearly marked continuous traffic lane will be an improvement over the current 1.75 lanes.
