Many offices in US, including the Indian embassy, have a queue system based on token. On arrival a person takes a token from the token dispenser (or the office clerk) with current time and a number on it. As the service window becomes availble, clerk call the next number in the queue. The person holding the token with the queue number just called gets the service next.

The police cars in US have their numbers (squad number) itched on the top of the vehicle. This helps in case of helicopter-assisted chase of suspects. The helicopter can use the squad number to refer to the police car in case of communications with the patrol cars chasing the suspects.

Wherever you go in US you will abundant use of "STOP" traffic signs, particularly at small junctions and at three-way and two-way junctions. There are either two-way or three-way or four-way "STOP" signs. Vehicles have to stop completely if they encounter "STOP" sign on their "way" and then they can proceed in the order in which they arrived at the "STOP" sign.

This is a very inexpensive way to control traffic at small junctions as installing traffic lights at every small junction is not feasible. Also, "STOP" sign serve to warn drivers of unexpected traffic, such as, of pedestrians crossing the intersection.