Live road traffic in Nantes

An area held by its crossings

Green marks a free-flowing road, orange heavy traffic, red congestion, grey an unusable reading. Around 860 main sections are instrumented.

The Loire governs the rest. The crossings are few relative to the flows they absorb: when they turn red, it is not one congestion among others — it is the whole area that seizes up.

The cyclist's problem: you cannot go around a bridge

On a saturated urban road, a cyclist almost always has an alternative — a parallel street, a quieter route. On a crossing, no: the structure is the only way through.

Hence the value of checking the map before setting off rather than once committed. Shifting your departure by twenty minutes, or aiming for another crossing, costs less than a bridge at a standstill.

What the planner does with it

Where Sécu’Cycle plans routes, this layer feeds directly into the safety score: for a comparable journey, it steers away from red roads when a credible alternative exists.

Frequently asked questions

Where does the Nantes traffic data come from?

From the “Fluidité des axes routiers” dataset published by Nantes Métropole on its open data portal, under the ODbL licence, and refreshed continuously.

Why does my street not appear on the map?

Because only main roads are instrumented, around 860 sections. Residential streets are not measured.

Can a red bridge be avoided by bike?

Rarely without lengthening the journey noticeably. That is why checking before you leave beats adapting en route.

Does traffic change the route suggested in Nantes?

Not for now, as route planning covers only Bordeaux and the Tournai area. Where it works, congestion feeds into the calculation.

Sources and licences

• Fluidité des axes routiers — Nantes Métropole · data.nantesmetropole.fr · ODbL

Each dataset and its licence are listed on the Data sources page.