Drive Time Maps and Catchment Areas: A UK Guide

What is a drive time map (isochrone)?

A drive time map - sometimes called an isochrone, from the Greek for "equal time" - is a polygon drawn around a starting point that contains every road location reachable within a given number of minutes. The shape isn't a circle: it stretches out along motorways and dual carriageways where you can cover ground quickly, and pulls in where the road network is slow, sparse, or interrupted by water and terrain.

From a typical UK city centre, a 30-minute drive time area looks lobed and irregular. From a town near a motorway junction, the same 30 minutes might reach twice as far on one side as the other. From a rural village down narrow lanes, the area is small and roughly symmetrical until it hits the nearest A-road, at which point it bulges outwards in that direction.

Open the Drive Time Map, enter any UK postcode, and you'll see the shape immediately - it's the clearest way to understand the concept.

Drive time vs straight-line radius - which to use when

A straight-line radius is a circle of fixed distance around a point. It ignores roads completely. Drive a radius and drive time area from the same starting point and the difference is usually striking.

Use a straight-line radius when:

• You need a quick, simple visual ("everything within 5 miles")
• The mode of travel doesn't matter or varies (walking, cycling, public transport, mixed)
• You're working with planning regulations or contractual definitions that specify a distance, not a time
• You're comparing many points and need a consistent, fast measure

Use a drive time area when:

• The realistic question is "where can I reach", not "what's nearby in a straight line"
• Your customers or staff drive to the location
• You're defining a delivery, service, or sales catchment
• The geography includes meaningful obstacles - estuaries, big hills, motorways without nearby junctions

A 10-mile radius around central Plymouth covers a lot of sea. A 30-minute drive time area around the same point covers nearly no sea but a much wider sweep of South Devon and Cornwall along the A38. The radius is mathematically simple; the drive time area is operationally useful.

How drive time is calculated

The calculation has three ingredients: a road network, a routing engine, and a set of assumed speeds for each type of road.

The road network comes from OpenStreetMap, the same crowd-sourced geographic database that powers many other mapping tools. OSM includes every motorway, A-road, B-road, residential street, lane, track, and footpath in the UK, along with restrictions like one-way streets, turn limits, and access rules.

The routing engine is OSRM (Open Source Routing Machine), which calculates shortest-time paths through that network. From the start point, OSRM samples journeys in every direction outwards, finding the boundary at which the travel time hits the target (5, 10, 30 minutes - whatever you choose). The points on that boundary are joined up to form the polygon.

Road speeds are based on the OSM tag for each segment - typical motorway speeds for motorways, slower defaults for residential roads, very slow for tracks and footpaths (which are excluded entirely for driving). The defaults are sensible averages, not posted speed limits or live observations.

Accuracy and limitations

Drive time areas are honest estimates, not promises. Here's what they account for and what they don't.

The tool accounts for: road geometry, road type (motorway vs B-road vs residential), one-way streets, turn restrictions, the actual road network in your area.

The tool does not account for:

• Live traffic. Rush hour in central Birmingham is not the same as 3am. The tool uses typical free-flowing speeds.
• Roadworks and closures. Temporary disruption isn't reflected.
• Weather. Snow, fog, and heavy rain slow real journeys. The tool doesn't know.
• Time of day. Same area drawn at 9am Monday and 9pm Sunday will be identical.
• Your specific driving. Some drivers are faster, some slower. Defaults are averages.
• Vehicle type. A van isn't a Porsche. Heavy or restricted vehicles can't use all the same roads.

In practice, the tool produces results that match a typical mid-day, mid-week journey within about 10-15%. That's accurate enough for catchment analysis, service area definition, and rough planning. It's not accurate enough to dispatch an ambulance or honour a 30-minute delivery promise.

Using drive time maps in UK industries

Here's where drive time areas earn their keep across seven typical UK use cases.

Estate agents

A buyer says they want to live within 30 minutes of their office in central Manchester. Don't draw a 10-mile circle - that includes most of Manchester city centre, a chunk of Salford, and arbitrary parts of the M60 ring. Draw a 30-minute drive time area from their workplace at 8am-ish reality. You'll see which suburbs, towns, and villages are honest commutes (Altrincham, Bury, Bolton, Stockport) and which look close on a map but aren't (parts of the Peak District that look adjacent but require a slow climb up the A6).

Field sales

A regional sales manager wants to know how much territory a rep can realistically cover from a base in Reading. Draw a 60-minute drive time area to see the working radius. Compare to the same area from Swindon, or Slough, and you'll find that "Thames Valley" looks very different depending on where you actually start. Field territories built on drive time areas keep journey expectations honest and quotas defensible.

Retail and franchise location

Where should the next branch go? The current ones each pull customers from their 15-minute drive time area, with some bleed at the edges. Drawing the drive time areas around existing sites shows where they overlap (cannibalisation risk) and where there's white space (potential growth). The right next location is one whose drive time area picks up underserved population without overlapping existing sites significantly.

Delivery zones

If you offer same-day delivery from a depot, your delivery zone shouldn't be a circle - it should be the drive time area for whatever round-trip time fits your operations. Define it as the polygon, share it with customers as a postcode list, and you avoid the awkward "but I'm only just over your line on the map" conversation. The Drive Time Map outputs the full postcode list as a CSV that drops straight into a delivery management system.

Tradespeople

A plumber, electrician, or builder needs to know where they can profitably take jobs. Below a certain drive time the work pays; above it, the travel eats the margin. Draw a 30-minute drive time area from your base and you've got an honest "I work in this area" statement for your website, Google Business Profile, or quote conversations.

Recruitment

Local employers competing on commute time can use drive time areas to see how big their realistic candidate pool is. A warehouse offering minimum wage needs a 20-minute catchment because nobody wants to drive longer than that for that pay rate. A specialist role at a competitive salary can pull from a 60-minute area. Knowing which postcodes fall inside that area tells you where to advertise.

Commute planning

House hunters weighing a job offer can use a drive time area around the workplace to see which towns, villages, and neighbourhoods sit within an acceptable commute. Add the postcode list to a property search filter and you've narrowed thousands of listings down to ones that actually pass the journey test.

Working with the postcode list

Every drive time area you generate on this tool comes with the full list of UK postcodes inside the polygon. The on-screen summary shows three numbers: postcode districts (the outward code, e.g. "M1"), postcode sectors (outward plus first digit of inward, e.g. "M1 1"), and full postcodes (e.g. "M1 1AE").

Districts and sectors are useful when you need a coarse view - an area with 100 districts covers a big chunk of the country; one with 5 districts is local. Full postcodes are what you need for operational systems: each one identifies roughly 15 addresses, so the count gives you a real-world sense of how many properties fall inside the area.

The CSV download is structured with three columns - postcode, district, sector - sorted by district then postcode. Sample rows:

postcode,district,sector
M1 1AE,M1,M1 1
M1 1AF,M1,M1 1
M14 4AA,M14,M14 4

That format drops straight into Excel or Google Sheets. Filter by district to see all postcodes in a city centre. Pivot by sector to see counts per neighbourhood. Match against a CRM export to flag which customers fall inside or outside a new delivery zone. Use it as a lookup table in a SQL query to attribute existing sales to catchments.

Common questions

Can I combine multiple drive time areas?

Not directly in the tool today - it draws one area at a time. The workaround is to generate each area separately, download each postcode CSV, and combine them in a spreadsheet (concatenate the rows and deduplicate by postcode). That gives you a union of all areas, which is what you usually want for a multi-site catchment analysis.

How does drive time handle ferries and tunnels?

OSRM treats ferries, the Channel Tunnel, and major road tunnels as part of the road network with timing baked in. The Mersey Tunnel, for example, adds a realistic crossing time to journeys between Liverpool and the Wirral. Ferries are slower and the timing assumes free-running, not waiting times, so cross-Solent or cross-Channel journeys are optimistic.

Why is my 30-minute area smaller than my actual 30-minute commute?

Almost certainly because you commute in peak traffic and the tool assumes free-flowing conditions. The tool's 30 minutes is more like a 9pm Sunday journey than an 8:30am Tuesday one. If you want to estimate your real commute, halve the time on the tool (i.e. draw a 15-minute area to approximate a 30-minute peak commute) - that's a rough rule that often works in dense urban areas.

Can I use this for cycling or walking catchments?

Not yet - the current version of the tool supports driving only. For walking or cycling catchments, switch to radius mode and use a straight-line distance as a rough proxy (a comfortable walking radius is about 0.5 miles in 10 minutes; cycling is about 2-3 miles in 10 minutes on flat terrain). Real walking and cycling areas are coming.

How accurate is "30 minutes drive" really?

The honest answer: within 10-15% of a typical journey for that area, accurate to about the nearest mile at the edges, and broadly correct in shape. For planning decisions that turn on tens of thousands of pounds (where to put a shop, where to define a delivery zone, whether to take a job 30 minutes away), it's accurate enough to base the decision on.

What it isn't: an answer to "will this specific journey at this specific time take exactly this long?" That question depends on traffic on the day, whether the M6 is closed, whether it's school pickup time, whether there's a Premier League match on. The tool doesn't know any of that, and pretending otherwise would be dishonest.

If you need traffic-aware journey times, use Google Maps for the specific route you care about. If you need a catchment area for planning, where you're answering "roughly where can I reach in 30 minutes from here", the Drive Time Map is exactly the right tool. The catchment changes with the time of day in reality; the planning conversation it supports usually doesn't.