See if you look at the exits the one on the left next to the bingo only goes left. The one in the middle of the road appears to only head to Culloden which then means the one on the right leaves you with 3 exits, one to sir walter scott drive, one to Drakies and one back to old perth road. However, if you use that lane it means you go from the middle of the roundabout and then back to the outside in a matter of seconds, it means that you cross over two lanes!
I wish I had a overview picture of that roundabout that I could take to the council and tell them to work that place out!