On the way in to work this morning, I was stopped behind about 3 cars at an intersection where I'm planning on making the right turn. Intersection has 1 left turn lane, 1 right/straight lane, and is No Turn on Red. The car in front of me had a right signal on; he passed me just before hitting the line of traffic so probably should have seen me signaling for a right, but may not have been paying attention. Light turns green, we all accelerate. I'm moving up just a bit on his right, but I've got no intention of passing there - I was sure he'd open it up as he accelerated beyond 10 mph. Except he didn't; he slowed down much more as if he was expecting me to pass on the right (and go straight through). Usually I encounter this when a car passes me planning to make a right turn, and realizes halfway through the pass that they don't have the room to do it; I'm riding straight through. I'll never pass on the right on that case; I'll come to a near stop behind or pass on the left as appropriate. But I wasn't quite sure what to do in this case - I certainly won't pass on the left to make a right turn, and he wasn't figuring out quickly that he should just go. I ended up passing on the right, but I wasn't very comfortable doing it.
Anyone else encounter this situation? Any advice?