Flawless driving conditions = Speed vans everywhere?

[Ranger 6]

F i F said:

...In fact on one day with very changeable weather I passed the van, conditions fine & it was operating, when I came back fifteen minutes later it was now raining and the operator was reading the paper and with a cuppa on the dash. A couple of hours later it was dry again, if black skies and he'd moved a mile down the road and was now operating. An hour later it was absolutely hissing down and he'd packed up and moved on....

Isn't that because the rain scatters the laser and renders it ineffective? (or am I spouting sh*te?) Come to think of it I've never seen BiB doing a roadside check in the rain either...

So ultimately is the reason there's the vans out in the sun is because they don't work in the rain?