Recently the city installed a number of new traffic cameras: rather than speed, these cameras focus on drivers blocking the box (being stopped across intersections), driving through crosswalks, and not coming to a complete stop at stop signs.
You may have seen them, they're big and blocky and on the side of the road, rather than the small ones that catch speeders. I spotted the one here on 11th near Lamont. They're a good thing to improve traffic flow and protect pedestrians, but they also mean that drivers need to be careful.
There were a few snafus with the roll out, namely that the city didn't give enough notice, so they've pushed back issuing tickets until February 1.
But in the meantime, you can check out the city's interactive map of where they are. In Columbia Heights, there's only a few, but some can be moved, so you may need to check back occasionally.