Bending the Chart to Fit the Road

Mapping Collision Density Along the A1

More than 350 years ago, cartographer John Ogilby transformed the way travellers navigated Britain. His famous strip maps turned the nation's principal highways into continuous journeys on the page, allowing travellers to follow routes such as the Great North Road stage by stage across the country. Today's A1 follows much of that same historic route between London and Edinburgh. However, where Ogilby reshaped the road to suit the map, A1 Collision Density bends the chart to follow the road.

This new visualization maps more than 24,000 reported traffic collisions recorded on the A1 and A1(M) between London and Edinburgh using data from the UK's STATS19 road safety database. Rather than simply plotting collision locations on a map, the data has been projected onto a reference line representing the route itself. The result is a bar chart that runs parallel to the road, with each bar corresponding directly to a specific stretch of the A1.

This deceptively simple design solves a surprisingly difficult visualization problem. Placing the data on a parallel curve that mirrors the road's actual path ensures peaks in the chart can be linked instantly to their geographic location.

The approach combines the strengths of both maps and charts. The bars make it easy to identify sections of the A1 with high numbers of reported collisions, while the map provides the spatial context needed to understand where those concentrations occur. Users don't have to switch between separate visualizations because the chart and the geography are integrated into a single view.

The visualization also works well across multiple scales. Viewed from afar, it reveals broad patterns along the entire London-to-Edinburgh corridor. Zoom in and it becomes possible to explore individual junctions, towns, and local hotspots. The chart remains tied to the route regardless of scale, maintaining the connection between the data and the geography.

Via: Quantum of Sollazzo