Cycling accidents in Nantes
This map places the injury accidents involving a cyclist recorded across Nantes Métropole between 2015 and 2023. It is instructive provided you know what it leaves out.
Interactive map in Nantes — cycling accidents.
The Nantes blind spot: tram rails
The BAAC register only records an accident that led to police involvement. An isolated fall, with no third-party vehicle, falls outside it. Yet in Nantes, a wheel caught in a tram rail is one of the classic ways to come off a bike.
Along the tram lines, the map is therefore systematically optimistic. Cross rails at right angles, widening your line if you must, particularly on wet ground.
Hot spots that are first of all forced passages
Zoomed out, the map aggregates accidents into a density; zooming in, each point separates and takes the colour of its severity — slight injury, hospitalised injury, fatal accident.
The sharpest clusters read where geography forces the passage. The Loire bridges and the Erdre crossings channel every cycling flow, and accumulate accidents in proportion.
From a red dot to route planning
Where Sécu’Cycle plans routes, each accident is attached to the road graph segments within a 25-metre radius, where it applies a penalty to the safety score. That penalty is capped, precisely because the data carries no exposure denominator.
Frequently asked questions
- Why so few accidents along the tram lines?
- Because a fall on a rail most often happens without a third-party vehicle, and therefore generates no injury accident report.
- How many cycling accidents does the map really record?
- Only those that led to police involvement. Falls on their own, minor collisions settled amicably and near misses are all absent.
- Does a red area mean the place is dangerous?
- Not necessarily. It marks a cluster of accidents, which also depends on how many cyclists pass through. A busy bridge accumulates them mechanically.
- How recent is the data?
- It runs to 2023. ONISR publishes the injury accident reports several years in arrears.
- Do these accidents change the routes suggested in Nantes?
- Not for the time being, as route planning covers only Bordeaux and the Tournai area. Where it works, they lower the safety score of the segments concerned.
Sources and licences
- « Accidents de vélo » — derived from the ONISR BAAC files, published by Koumoul · data.gouv.fr · Licence Ouverte 2.0
Each dataset and its licence are listed on the Data sources page.