I know not everyone supports bike boxes, and I'm not sure that I do either. But I'm thinking about it at the moment because our city engineer mentioned to some of us that he was contemplating putting one in at an intersection here, and wondered what we thought about it. So we are trying to evaluate. It would be our first one here in Portland, MAINE.
Personally, in this situation, I'm probably going to recommend against it. It is a signalized intersection with 3 lanes: Left turn only, left turn/through, and right turn/through. So to go straight, all you have to do is move into the center of the nearest lane. To turn left, you need only move over one into the middle lane, and then into the left side of it. It's flat, and the traffic is probably in the mid 30 MPH range, but of course slowing down approaching the light. Relatively easy, as channelized intersections go, so I don't think any fancier and potentially more confusing infrastructure is warranted.
So that got me thinking, when is a bike box warranted, according to its proponents? Some particular mix of more challenging traffic speeds and/or intersection geometry? An uphill approach? What specific problem is the bike box trying to solve? Or do proponents advocate a bike box solution for every intersection?