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AADF and AADT – Annual Average Daily Traffic
AADF means Annual Average Daily Flow. The Department for Transport defines it as the average over a full year of the number of vehicles passing a point in the road network each day.
AADT means Annual Average Daily Traffic. The term is widely used in transport work for a comparable annual daily traffic measure, but the Department for Transport’s Great Britain road-traffic statistics use the term AADF.
You can explore DfT count points and annual flows on the Road Traffic Statistics service.
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How is AADF calculated?
Conceptually, AADF represents annual traffic spread across the days of the year. In the national DfT dataset, however, you should not assume every year’s figure comes from a continuous 365-day count at that location. DfT combines manual counts, automatic count data and estimation methods to produce annual traffic estimates.
The count-point record therefore matters. The DfT service shows the traffic estimate together with information about the count method and the road link.
How can AADF or AADT be used in planning?
Annual traffic information can help establish the general scale and composition of traffic on a road. Depending on the proposal, it may be relevant to:
- transport assessments and transport statements
- development access and highway design
- traffic growth and junction analysis
- noise and air-quality assessments
- road-safety and pedestrian assessments
- understanding HGV, car and other vehicle flows
AADF is not a substitute for every form of traffic survey. A planning application may need peak-hour counts, turning movements, speed data, pedestrian surveys or other site-specific evidence.
AADF compared with AAWT and ASDT
AAWT focuses on average weekday traffic, while ASDT is a seasonal summer measure used in some traffic studies. AADF instead represents an average across the full year.
Which figure matters most depends on the planning question. A tourist destination with a strong summer peak, for example, may need seasonal evidence in addition to the annual average.
AADF and AADT Page Updated: 27th August 2026