What an isochrone is and how to use it

Draw a one-kilometre circle around your premises on a map. Now try to cross it on foot. If there's a river, a motorway or a railway line in the way, you'll find that half of that circle is unreachable. A customer doesn't walk in a straight line. They walk along streets. That's what an isochrone is for.

What an isochrone is (and what it isn't)

An isochrone is the area of the map you can reach from a point within a given time (5, 10, 15 minutes) along the real street network. The word comes from the Greek "iso" (equal) and "chronos" (time): every point on the boundary is the same distance away in time, not in metres.

It isn't a circle. It isn't a straight-line distance. It's calculated on the real street network, using a typical speed for the mode of transport you choose (no real-time traffic). If there's a park with no way through between your premises and a neighbourhood, that neighbourhood is left out, however close it may be as the crow flies.

Circle vs. isochrone: why the difference matters

A 1 km radius draws a perfect circle on the map. Pretty, but misleading. The 10-minute walking isochrone from the same point usually has the shape of an irregular blob: it stretches out along the avenues with pedestrian crossings and stops abruptly where there's a railway line, a river or a steep hill.

The practical result is the same in Madrid, Paris, Lisbon, Milan or Berlin: the 1 km radius and the 12-minute walking isochrone can contain very different numbers of residents, especially where a river, a park or the railway tracks split the neighbourhood in two. And the residents you see inside the circle but outside the isochrone aren't your customers: they'll never reach you on foot.

Which time and which mode to choose for your sector

There's no "correct" time: it depends on why your customer is moving. The time and the mode of transport completely change the analysis. These are the ranges that, in practice, tend to work:

• Neighbourhood café or bakery: 5-10 minutes on foot. Any further and the customer prefers the café right below their flat.
• Gym or yoga studio: 10-15 minutes on foot or by bike. A daily habit, people don't take the car.
• Destination restaurant or specialist shop: 15-20 minutes by car. People travel there on purpose.
• Dental or veterinary clinic: 10-15 minutes by car on weekdays, up to 20 on Saturdays.
• Home delivery by motorbike: 8 minutes maximum. Any longer and the food arrives cold or the flowers wilted.
• Education provider (tutoring centre, nursery): 10 minutes on foot for nursery and primary; 15 minutes by bike or by car for secondary and adults.

From the isochrone to the people

The blob on the map on its own is useless. What changes decisions is cross-referencing that blob with demographic data: how many people live inside, what their average age is, what income, what level of education. The same 10-minute walking isochrone can contain a few thousand residents or several tens of thousands, depending on the type of area.

Imagine two identical bakeries (this is an illustrative case, with round numbers to make it clear). One is in a well-established central area and within a 10-minute walk reaches, let's say, around 30,000 inhabitants/km² with a high average income. The other is in a residential suburb and within the same 10 minutes reaches perhaps 8,000 inhabitants/km² and a lower income. The map looks similar. The business isn't. The real figures for your area come from the official sources for each city.

3 common mistakes with isochrones

• Using the wrong mode. Calculating driving isochrones for a neighbourhood café overestimates the reach, because nobody takes the car for a €2 coffee.
• Exaggerated times. A 30-minute walking isochrone sounds ambitious, but it doesn't reflect your real customer: nobody walks half an hour for an impulse purchase.
• Not comparing with the competition. Your isochrone overlaps with the one belonging to the competitor on the corner. If you don't subtract the area your rival covers, you're counting the same people twice.

How it's calculated in POINOVA

You drop a pin on the map, choose the travel time and mode of transport, and POINOVA draws the isochrone and instantly returns the population, average income and share of young and older residents inside it; with Pro, you also get education and the competition. Demographic data from each country's statistics institutes, with the source cited. No downloading anything, no cross-referencing tables by hand.