.....there is a rumour they aren't even active. The short cut you mentioned and another one you can join after the start of the average speed section corrupt the accuracy of the cameras such an extaent that you can turn off, maintain the max speed along the short cut, rejoin and still be over the max average speed on the main road. Motorcycle News proved it just after they were erected. However, I wouldn't like to have to argue that toss in court so 'they' win this one.