In my little NJ town, a policeman (and former Marine) was killed this year generating revenue. They had him park, lights out, on a dark shoulder, just over a rise on a major highway, clocking speeders. His car was crushed like a soda can when an eighteen-wheeler rear ended him without ever hitting his brakes. Died instantly.
The driver of the truck tested negative for everything, but was still charged with vehicular homicide. Trial pending.
You may think the driver of the truck "tested negative for everything," but it sounds like he failed one important test: He drove his truck outside the travel lane of the road.
That doesn't justify the idiocy of having a police car parked on a shoulder for the purpose of generating revenue, but it does explain the vehicular homicide charge.