I made an interesting observation with the Beaverton radar vans last night.
If you have ever seen the vans at night, you know that the speed sign on the back of the van is like the sun at noon day. When that thing lights up it gives everyone within a quarter of a mile ample warning. I ran across the vans last night and made a very interesting observation. The operators position the display parallel to the road so it isn’t easily seen by the cars as they approach the van.
Notice that from the back of the van they aren’t shining a spotlight from the speed indicator.
From the side you can see the speed indicator.

Same deal on Beaverton-Hillsdale Hwy.
So, I think the days of getting a long distance warning  at night are over. The good illumination from the speed indicator will be replaced by the blinding flash as the van takes the pictures.