By Charles Pekow — How can we minimize delays and conflicts among bicycles, buses and other right-turning vehicles at corners? Portland State University in Oregon took a look at interactions between the three classes on a corridor in its home town. The site in question included a bus stop, bike lane and bike box, and a lane reserved for buses and right-turning motor vehicles.
It seems that if cyclists rested in or behind the box (such as when the box is filled with other cyclists), they didn't interfere with buses. Nor did they if they crossed the intersection ahead of a bus. Most boxes are painted green and since cyclists in them wait in front of the turn lane, they don't interfere with those turning. The report says “it is a welcome finding that they do not burden bus flow.”
See Evaluation of Bus-Bicycle and Bus/Right-Turn Traffic Delays and Conflicts at https://trid.trb.org/view/1664994.