When an officer writes a ticket, he signs it with his name and his badge number (or whatever his personal number is called in his agency). Finding his station is a piece of cake. A call to directory assistance with the name of the law enforcement agency shown on the citation (highway patrol, county sheriff, or whatever) is enough to get a foot in the door. Once the agency is contacted, they can refer the caller to the correct telephone number for the subpoena clerk serving the geographical area where the traffic stop was made.