A1 Collision Density

The A1 is Great Britain's longest numbered road — 410 miles from central London to Edinburgh, passing through the East Midlands, Yorkshire, and Northumberland before crossing into Scotland. This visualization maps every reported road traffic collision along the route from 2000 to 2024, revealing where the road is most dangerous and how collision density has shifted over 25 years.

Each bar in the histogram represents a segment of the route. Taller bars indicate stretches with higher collision rates — often corresponding to complex junctions, urban sections, or areas where the road transitions between motorway and single carriageway.

Data Source

Collision data comes from STATS19, the UK's official record of road traffic collisions reported to the police where at least one person was injured. The dataset covers 2000–2024 and includes location, severity, time of day, and number of vehicles and casualties per incident.

Published by the Department for Transport (DfT): Road Safety Open Data. Contains public sector information licensed under the Open Government Licence v3.0.

Methodology

Collisions are filtered to those recorded on the A1 (first_road_class 3) and A1(M) (first_road_class 2) with first_road_number 1. Each collision is projected onto a reference polyline representing the full A1 route, and counts are aggregated per segment to produce the histogram.

Map

Map tiles provided by OpenFreeMap using MapLibre GL JS, based on OpenStreetMap data.

Built with

VisQuill — a reactive vector graphics framework for interactive data visualization. visquill.com