The laser distance has a maximum of 1000m (theoretical).
Most of the mobile speed vans with the average equipment used by most counties police will ping you with laser at furthest they can, then will wait until you're closer to photo license plate (on a bike you have to ride past the van for them to photo back of bike), as the theoretical distance for there camera's is only 500m but in actual is about 250m for the plate to be readable (and thats a standard UK legal plate size)
I actually appealed one once and got it squashed. I argued that because I had no license plate on front of vehicle the bike pinged from the front could be a different bike photo'd from behind passing the police van. My bike, helmet and leathers were all readily common equipment. I was only doing 37 in a 30 so perhaps they just didn't want the hassle lol.
Theres 2 hot spots they park around my way, both places you can't see them until your about 50m away. usually find a friendly car driving will flash lights.