Yeah, had that on the M6 roadworks on the way back from the Airport this evening. Going no faster than 40 and boards lit up like a Christmas tree telling me to slow down
Also found that my car sets off a speed camera on the opposite side of a dual carridgeway when I'm nowhere near it and sticking to the limit - I'm not even on the lines Suppose it could be that the camera is in dip and when it flashes I'm about level with it in height.
My Zafira sets off speed boards too! I was in a convoy of traffic on the A140 going through some middle of nowhere village. None of the other cars set off the board except mine and I was travelling slower than the cars in front.