The lines, with no sign of a camera mount near them, probably mark a calibration point for a mobile camera (including laser or vehicle-mounted) system.

It's not the vans/cameras that cause the problems, it's the people's reactions to them

Which is usually the same when they see a traffic womble parked on the hard shoulder of the motorway and slam on...

Which is usually the same when they see a traffic womble parked on the hard shoulder of the motorway and slam on...

That's only to see if there are any limbs in the road.