How commute times are calculated

Most town comparison tools measure a straight-line distance between two centre points. Icioola computes an itinerary: the walk to the stop, the wait, the transfers, then the walk at the other end. It is the only way to get a figure that resembles your actual day.

The starting point is not the centre of the town

A town is not a point. Taking its geometric centre means starting from the middle of a field or a forest while the population lives elsewhere. Icioola starts from the barycentre of real addresses (Base Adresse Nationale). For Rambouillet, that correction alone brings the commute to Paris from 105 minutes down to 88 — the old figure was not cautious, it was wrong.

Public transport: a calculation, not an estimate

Timetables come from the GTFS feeds published by the transport authorities (Île-de-France Mobilités, SNCF, city networks), merged and then routed by an itinerary engine (r5py, R5 core) over the IGN pedestrian network.

• Departing 8:30 on a Tuesday — an ordinary working day, at peak time.
• Walking included at both ends, on the real street network.
• Transfers and waiting counted, using that day's actual frequencies.
• Two values are computed: the median journey and a bad day (9 journeys out of 10 are shorter). The median is the one displayed.

By car: real road routing, everywhere

Car time is not a distance converted into a duration: it is computed on the real road network. It already was inside the 22 areas — the same engine that timetables transit also routes cars there, across every pair of towns. Since 19 August 2026 it is computed for the 34,746 towns of metropolitan France too, through a second routing engine (OSRM) over OpenStreetMap roads. Checked against Michelin times on known journeys, the distance gap is under 1 %.

These durations ignore traffic. They assume a clear road: no congestion model, no jams, no roadworks. Measured against Michelin they come out 6 to 15 % faster — a systematic gap, not a random one. At rush hour, allow more.

Bike and walking: usually estimated, and we say so

These two modes are also routed on the street graph inside the 22 areas, but coverage there is thin — one pair of towns in twelve by bike, one in fifty on foot — because beyond a few kilometres the engine stops connecting the points. Wherever the routing is missing, the time is estimated: straight-line distance increased by 30 % (the detour of a real network), divided by an effective speed — 14 km/h by bike, 4.8 on foot — plus a fixed start-up cost. Usable to compare two towns against each other; not a substitute for a satnav on a Tuesday morning.

Where the calculation exists, and where it does not

Transit commute times are computed in 22 areas, each covering the whole département rather than the urban authority alone:

Bordeaux et la Gironde · Brest et le Finistère · Clermont-Ferrand et le Puy-de-Dôme · Dijon et la Côte-d’Or · Grenoble et l’Isère · Île-de-France · Lille et le Nord · Lyon et le Rhône · Marseille et les Bouches-du-Rhône · Metz et la Moselle · Montpellier et l’Hérault · Nancy et la Meurthe-et-Moselle · Nantes et la Loire-Atlantique · Nice et les Alpes-Maritimes · Orléans et le Loiret · Rennes et l’Ille-et-Vilaine · Rouen et la Seine-Maritime · Saint-Étienne et la Loire · Strasbourg et le Bas-Rhin · Toulon et le Var · Toulouse et la Haute-Garonne · Tours et l’Indre-et-Loire.

Everywhere else, the commute shown is now the car one, computed town by town across the 34,746 towns of metropolitan France. It works as a filter rather than a mark: it decides which towns stay in the running, and never inflates a rating. Overseas France has no commute time at all — no road connects it to the mainland, and a shared road matrix would be meaningless there; quality of life, meanwhile, is compared everywhere.

What the figure does not know

It knows nothing of roadworks, strikes, your exact arrival address within the destination town, or the school drop-off. It assumes a departure at peak time: at 9 p.m. the same town can become far more remote — which is why the town page also shows the time of the last departure. Take it for what it is: an order of magnitude comparable from one town to the next, not a promise to the minute.

And tomorrow?

In the Paris region a second ranking is computed on the network as it will be in 2030, Grand Paris Express included: some towns gain more than thirty minutes. It is shown next to today's ranking, never instead of it.

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