What the figures mean—and what they do not

Official source

We use the Department for Transport Road Traffic Statistics bulk downloads: count-point locations and Annual Average Daily Flow (AADF). The source covers Great Britain. Data is reused under the Open Government Licence v3.0.

DfT downloads page ↗ · Open Government Licence v3.0 ↗

The daily number in plain English

The headline number is the estimated number of vehicles passing an official location in both directions on an average day of the year. Its technical name is Annual Average Daily Flow (AADF). It is not a live counter, a peak-hour figure or a measure of congestion.

How the map colours work

The coloured lines follow numbered roads from the basemap. For each nearby road, we combine its available official locations into a typical daily figure and a simple comparison: Lower traffic, Typical traffic or Higher traffic. Click a coloured road to open the nearest official estimate used in its summary. A road can vary along its length, so the detail page identifies the exact location behind that figure.

Counted and Estimated

Counted means the figure for that location and year is based on a traffic count. Estimated means DfT used an estimation method—for example, carrying forward a previous year or estimating from another observation. The detailed method from the source row appears on every count-point detail view.

How the data is processed

1. Download the current official zipped CSV files.
2. Validate every required column and stop if the schema has changed.
3. Detect the newest available year rather than hardcoding it.
4. Join the current count-point inventory to all AADF history.
5. Keep road, junction, coordinates, method, link length and vehicle classes.
6. Identify the most recent year marked Counted.
7. Calculate comparison percentiles and useful area summaries.
8. Write a versioned overview, ID index and compact spatial shards.

The generated release is 2025-3eaa43f6de, processed on 21 August 2026. The two official ZIP files are hashed so a changed source produces a new release identifier.

How the comparison works

We rank the latest daily motor-vehicle estimate among all current locations with the same DfT road type: Major or Minor. The detailed data uses five equal bands; the map combines the bottom two as Lower traffic, the middle band as Typical traffic and the top two as Higher traffic. These labels are relative comparisons, not health, safety, planning or congestion thresholds.

Important limitations

• DfT estimates every major-road link in Great Britain but samples only some minor roads.
• A residential street may not have its own count point.
• Individual links and small areas are less robust than regional or national statistics.
• Older counts may be carried forward or adjusted; check the method and last counted year.
• Coordinates mark the count point or road link, not an address.
• Straight-line distance is not walking or driving distance.
• Pedal-cycle estimates can be especially variable at individual sites.
• More recent local highway-authority data may sometimes be more suitable.

Geocoding and maps

Postcodes.io converts a postcode to an approximate centre using official postcode data. OpenFreeMap supplies the configurable basemap, with OpenStreetMap data and required attribution displayed on the map.