At the beginning, Martha's blue car shows the back license plate K2W DT7. When Marion walks to his office, Martha drives past, and the license plate says B5G NS1.
All the vehicles shown in Tennessee have front license plates. The state only issues rear plates.
Ray says a trucker had spotted Darla and the pickup she stole at a rest stop and State Police rolled up Code 7. In American Law Enforcement, Code 7 means meal break. If anything, they would have rolled either Code 2 (non-emergency, lights/no siren) or Code 3 (emergency, lights/siren authorized).