There's a very similar intersection in our small town, only it has five roads converging instead of three. There are the same angled green arrows for the lane that curves to the right, a normal green light for a center lane that goes straight, and a red for both lanes with no "No Turn on Red" sign. No one ever goes through on the angle on red. That lane is treated as a 'straight through' lane.

On the straight road I travel on, there is an intersection with a road on the left. At the lights, the name of the straight road changes from Platt to Huron, but the road off to the left is also Platt. Platt clearly used to be a straight road with Huron meeting it at a T, but they redeveloped the intersection to change priority.

Does this mean that when driving along Platt, if I stay straight and go onto Huron, I can go on red because it's technically a turn, even though there's no turning involved? I've always thought it would be sensible to be able to do this, but no-one ever does.

I believe it to be a curve upon visual inspection, including the semi-turn green arrows. However, if the road that dead ends at this intersection, causing the need for the traffic light in the first place, also has a traffic light, then the argument can be made that although the road it intersects is a curve, it should be treated as a turn for the benefit of properly providing the right-of-way to the dead-end road traffic that will be traveling onto the fucked-curve/turn road.

That, as far as I know, is the general rule. Although I think I'm one of the few people who actually obey that law.

The only way to clear it up is contact your local department of transportation for the jurisdiction in which this intersection exists, and ask them to clarify by posting directive signs.