Coming back from Perth this morning I noticed a traffic car parked up on the northbound hard shoulder just around the bend from the Bridge of Earn slip road and the cops looked like they were using a hand-held radar gun.

It's a good place to catch speeding cars because it's a long fast sweep and they would be out of sight till you were zapped but I've never seen them do that on a motorway before, (they were not on one of the Police Only humps) and I'm not sure how safe they would be, standing at the back of their car.

Could it be anything else they were using?