A DHL truck is blocking the view of the traffic light. But don’t worry, city of Boston has traffic lights for all obstacles.
A cab driver pointed this one out late one night while sitting at a red light on my way back to Brookline when traveling through Kenmore Square behind Fenway Park. There are more arrows outside this street view image. The engineer needed to make it clear, that green means you can go in any direction. (thanks to Christian S)