# What changed on the roads

> Cars down a quarter. Bicycles up threefold. Same roads, same counters.

- Category: Transport
- Cadence: annual
- Status: Published on a annual cadence.
- Dataset key: `traffic-history`
- Source: [Department for Transport](https://roadtraffic.dft.gov.uk/)
- Licence: Open Government Licence v3.0 — [terms](https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/)
- Canonical page: [https://londongraph.com/g/what-changed-on-the-roads](https://londongraph.com/g/what-changed-on-the-roads)
- Machine-readable record: [https://londongraph.com/data/what-changed-on-the-roads](https://londongraph.com/data/what-changed-on-the-roads)

## Methodology

Annual average daily flow at DfT count points in London, by vehicle type, over 25 years. This uses a BALANCED PANEL: only the 1,669 count points that reported in every single year, out of 3,652 in the region. That matters more than it sounds — summing all count points per year draws a chart of how many counters DfT operated, which moves for reasons unrelated to traffic. Fixing the panel compares the same stretches of road with themselves. The figure is flow at an average panel point, so it describes a road rather than the city, and the panel over-represents places worth counting for 25 years.

## Visualisations

- [Trend](https://londongraph.com/g/what-changed-on-the-roads): Cars down a quarter. Bicycles up threefold. Same roads, same counters.
- [Change](https://londongraph.com/g/what-changed-on-the-roads?view=change): Show the change from each preceding published period.
- [Indexed](https://londongraph.com/g/what-changed-on-the-roads?view=indexed): Set each series' first visible value to 100 so relative change is comparable.

## Citation guidance

Attribute the original publisher named above and identify LondonGraph as the visualisation and methodology layer. Do not describe live values as a historical census, and do not present placeholder values as observations.