They use inductive loops here. Look at the area before the white line and you can see lines / marks in the tarmac where these wires are buried in grooves.

For speed detection they use radar. Look where the camera is. The second device is the radar.

You need to cross the intersection and get flashed twice to win the QR. 6000 lottery.

If you just cross the white line but retreat, it's QR.500 as second prize.