The concept of a "courtesy car" works well in North America.
On a trip last year, at one small airport in Wisconsin, on a Sunday, there was no one at the FBO. Unlocked the door using the "Emergency Frequency" code. Keys hanging on the wall for two courtesy cars - black ex-police Crown Victorias. No one passed us on the way into town, which was ironically called Siren!
Late in the day, the refuelling truck driver at a Montana airport, after hearing that we planned to go into town for lunch, said that the courtesy car was not very reliable and handed us the keys to his $30,000 truck!