When driving around in a truck, i noticed, that (some?) police cars are invisible. The loot is spawning (some floating) and i wasn't able to move through it with the truck.
i came across 4 of those police cars on my latest journey, which makes me think all police cars might be invisible.
(if i remember correctly i was able to walk through those cars, so maybe its only buggy loots spawns coupled with buggy truck colisions)