Final answer:
Serial numbers on back door tags should be recorded for security and tracking purposes, such as recovering stolen vehicles and monitoring traffic flow using technology.
Step-by-step explanation:
Serial numbers on back door tags should be recorded for security and tracking purposes. In the context of technology, this practice helps law enforcement officials track stolen vehicles and catch suspects by having a record of the unique serial number associated with each vehicle's back door tag. Additionally, recording serial numbers can assist in monitoring traffic flow and other purposes, such as toll collection using transponders attached to vehicles.