Track and trace

Track and trace is a record that lets anyone follow an item backwards and forwards: which line made this packet, which mechanic fitted this part, where this batch of plastic was sent. It is also called traceability. Its purpose is to find exactly which items are affected when something goes wrong, and to prove where each item came from.

Here is how it works in general. Every item or batch gets an identity, such as a serial number, a batch number, a barcode or a radio tag. At each step of making, moving or fitting it, someone or something scans that identity and records the date, the place, the person or machine, and the materials used. All these records are linked together. Later, a person can start from any one item and see its full history, or start from one faulty ingredient and list every item that used it.

A trace can run in two directions. Tracing back starts from a faulty item and finds its parts, batch, line and operator. Tracing forward starts from a faulty batch of material and finds every item and customer that received it. The level of detail also matters. Tracing by batch tells you that 5,000 bottles are affected. Tracing by serial number tells you which 12 of them are. Finer tracing costs more scanning at every step, so makers choose the level by the harm a defect can do. An aircraft part is traced down to the single item. In Europe and the United States, so is each pack of a prescription medicine. A bag of flour is traced only to the day's batch.

Take, for example, a medicine maker that finds a bad batch of an ingredient. With track and trace, it can list the exact bottles that contain it and recall only those; see serialisation. Consider a food company that must show the farm each lot of milk came from, as in food traceability. For instance, an aircraft operator must prove that each engine part is genuine and has been fitted by a certified mechanic. This record is kept in maintenance software.

Without such records, a company that finds one defect has to recall everything it made, which costs far more. The same records also support the digital thread, which links a product's design to its making and repair.

How is it different from the digital thread? Track and trace follows where a physical item went and who handled it. The digital thread links the information about the product, such as design, specifications and changes.