DfT > AADFs > Caution

Cautionary Note

Annual average daily flows for some vehicle types such as HGVs, buses, motorcycles and in particular pedal cycles should be interpreted with caution because of the small sample sizes on which they are based.

For some count points on the trunk road network, there may be differences between the traffic flows shown and those from other sources, including the Highways Agency (HA).

The figures on this web site are derived from the Department for Transport's National Road Traffic Survey that aims to provide robust estimates of traffic by vehicle type, road class, and geographic area, across the whole of Great Britain's road network. The estimates are derived from a combination of automatic traffic counters and manual traffic counts, together with road lengths.

As part of the ongoing programme to improve the quality of the road traffic estimates, work is underway to compare the two sources and methodologies used. Further details about the DfT's traffic estimates are available from roadtraff.stats@dft.gsi.gov.uk.

Since publication of the annual Transport Statistics bulletin Road Traffic Statistics 2006 in July 2007, the Annual Average Daily Flows have been revised.