Dean, Photo Radar are always in Van(always GMC/Chevy Astro). And you can always see the tripod(for flash light) sits in front of the Van(from under the car when you are some distance away from the van, approach from behind)....

As for the Warning signs...it really depends...sometimes there are fixed camera(speed trap), but 90% of the time, it's just a warning sign, nothing more..

Andy Kuo