I was told on the one I attended, that the smart motorway are recording all the time. So if the signs are off and you are above the national speed limit ie. 70mph then the cameras don't flash but still record speed . If the speed signs are on limiting the speed to what ever is set , then they flash if above that speed . Theres a section of motorway at Newport South Wales that's notorious for dropping the speed limit for one section in the smart zone . So you come up to the smart zone it's set at say 50mph , you set cruise control or speed limiter for that speed then you come up to the section by the golf club and for about 100 yard they drop it to 40mph, then immediately back to 50mph, I swear that section alone funds the Welsh economy! They would argue that it's safety for the slip road, but its like being in a disco with the strobe lights on going through that section !!!!