Glossary

CAN bus — the vehicle's internal network. A device wired into it reads far more than one in the diagnostic port, including manufacturer-specific data and consumption calculated by the engine.

Diagnostic trouble code — a standard identifier raised by a control module when something is wrong. Comes in pending, confirmed and permanent states, only some of which mean act now.

Engine hours — running time rather than distance. Diverges sharply from the odometer in urban work, which is why distance-only servicing under-services city vehicles.

State of health — a battery's remaining capacity against its original, on electric vehicles. Determines both usable range and residual value.

Unscheduled maintenance — repairs that were not planned. Tracking it separately from scheduled spend is how you find out whether condition monitoring is working.

Utilisation — days a vehicle was used against days it was available. The measure that finds vehicles you are paying for and not using.

Vehicle off road — days a vehicle could not work. The cost nobody owns, because maintenance counts repair spend and operations counts missed work.

Walkaround check — the pre-use inspection. A legal requirement in commercial transport, and the complement to telematics rather than a duplicate of it.

Whole-life cost — everything a vehicle costs from acquisition to disposal, including downtime. The basis for replacement decisions, and rarely assembled.

Terms used loosely by vendors

"Real-time" means transmitted at an interval. Ask what the interval is and what happens without coverage.

"Reads engine data" is a category, not a field list. Ask which parameters, on which model.

"Predictive maintenance" usually means threshold alerts on usage. Genuine prediction from failure patterns is rarer than the phrase suggests.

"Compliant" describes your configuration and records, never a product.

"Fleet savings of N percent" comes from a case study of a fleet that was worse run than yours.

How to read these notes

Start with the foundations if nothing is deployed — particularly what the vehicle reports and where the data comes from.

Start with cost if you need the number that justifies anything.

Start with condition if the fleet is breaking down and you want that to stop.

Start with the boundary note if driver monitoring is being proposed alongside.

Nothing here is legal advice, and the notes say so where it matters.

On the absence of numbers

How to treat any figure in this collection.

No savings percentages are quoted, because they depend entirely on how the fleet was run before.

No service intervals, which come from the manufacturer for your model.

No consumption figures, which depend on the vehicle, the load and the work.

Every number worth having is one you produce from your own fleet, and the notes say how to produce each.

Connect policy and data

The choices in this note can be compared with open the policy example. Keep the written purpose in control and enable only the information needed at this boundary.