The ages - old habit of letting a big rig engine idle is coming to a stop, at least in the major cities & truck stops. In Caliphonia nowadays, the smog cops patrol the truck stops and highway rest areas, writing tickets and making them shut them off. Many trucks now have a small diesel engine on the frame under the sleeper; it supplies power for the climate controls in the sleeper with little fuel use. The Jubitz truck stop in Portland, OR., among others, has a climate control system that you roll up into the passenger - side window; it has duct work and controls on it.
It is still common practice to leave a diesel engine idling in the winter, even though the chance of the engine freezing up is minimal. I leave my work truck engine idling while hanging chains so my extra pairs of gloves & socks can stay warm on the cab.
While railfanning Willamette Pass in the Oregon Cascades a few years ago, I encountered mechanical problems with my pickup in an area where cell phone coverage was spotty. A EwePee high - railer stopped to help. He made sure to re - start his engine when he turned on his linear booster so my wife's cell phone would receive better. The M of W guy said EwePee had installed the linears as part of a lap - top computer track warrant system they were trying out; he also said it wasn't as reliable as a good old Motorola.