What heavy-vehicle counts support
Heavy-vehicle volumes can inform traffic engineering, freight planning, road design, traffic-impact studies, pavement inputs and intersection analysis when the class definitions and observed period match the decision. A count is evidence about the defined scope, not a universal freight forecast.
Categories must be project-defined
Rigid or single-unit truck
A truck body without a separately articulated semitrailer; the project definition should state how rigid body types are treated.
Articulated truck / semi truck
A tractor and semitrailer combination, often described as a tractor-trailer or semi; the visible combination must support the class rule.
Delivery or box truck
A commercial vehicle with a cargo body; distinguish it only when the study scheme needs the body-type detail.
Dump or construction vehicle
A project-defined construction or dump category where the body and use are observable and relevant.
Tanker
A vehicle carrying a tank body; tank appearance may be visible while exact use or load is not.
Multi-axle vehicle
An axle-based category requiring a source view that makes the relevant axles observable; do not infer axles from an obscured side view.
Terminology and ambiguity
HGV, heavy vehicle, commercial vehicle, freight vehicle, rigid truck, articulated truck, semi-trailer and tractor-trailer can be useful search terms, but they should not be treated as synonyms without a written project definition. A vehicle’s visible body does not always reveal its axle configuration, load or use.
Video classification considerations
Camera position, lane angle, distance, overlap, obstruction, lighting, weather and trailer visibility determine which cues can be observed. If the source cannot support the required distinction, use an approved unknown/exception treatment or revise the class scheme rather than guessing.
Quality-control checklist
- Approve the category dictionary and edge-case rules before observation.
- Reconcile heavy-vehicle classes with all-vehicle totals for each interval.
- Review high-volume, overlapping and difficult-light periods against the source.
- Keep body-type and axle-based outputs clearly labelled.
- Record source limitations and approved exceptions with the delivery.
Frequently asked questions
Can a count separate rigid and articulated trucks?
Yes, if the project defines those classes and the observation source makes the distinction reliable.
Are freight counts the same as heavy-vehicle counts?
Not always. Freight can be a purpose or vehicle-use category; heavy vehicle can be a physical or project-defined class.