Why subway maps look the way they do

How Harry Beck's 1933 Tube diagram and Vignelli's New York map shaped transit maps, how to read lines and transfers, and how GONOM draws its own.

The problem with a true map

The first maps of London's underground railways were drawn the obvious way: coloured lines laid over a street map of the city. That worked while the network was small, but it scaled badly. In the centre, where lines and stations cluster, everything was squeezed into a tangle; out in the suburbs, stations sat far apart across mostly empty paper. The parts of the map passengers needed most were the hardest to read.

The underlying insight is simple. Below ground, a passenger cannot see the streets and does not steer the train. What they need to know is which line to take, in which direction, how many stops to ride and where to change. Exact distances and the true curve of a tunnel matter much less. A map built around those questions can afford to bend geography, as long as it keeps the order of stations and the connections right.

Harry Beck's diagram

Harry Beck was an engineering draughtsman who had worked in the London Underground Signals Office, drawing schematics for electrical systems. In 1931, while out of work, he sketched a different kind of Underground map in his own time. He drew every line with straight segments, only horizontal, vertical or at 45 degrees, spaced the stations roughly evenly, enlarged the crowded centre at the expense of the outer districts and gave interchange stations their own mark.

The design was at first turned down as too radical, because it did not show relative distances. Beck revised it, a trial run of 500 copies went out through a few stations in 1932, and the first pocket edition followed in January 1933. Passengers took to it quickly, and the London Transport Museum records a first print run of 750,000 copies that year. Beck kept refining the diagram until his last version in 1960, and many systems around the world have since adopted the same grammar of straight lines and fixed angles.

Vignelli's New York and the great debate

The most famous argument about the idea took place in New York. In 1972 the transit authority introduced a subway diagram by the designer Massimo Vignelli, drawn on a grid with lines at 45 and 90 degrees and with stations moved where needed to fit it. To keep the focus on the system, water was coloured beige rather than blue and Central Park was shown in grey rather than green.

Many riders disliked it. In a city where people walk between stations and come up into streets they need to recognise, a map that did not match the ground felt wrong. In 1979 it was replaced by a geographic map designed by a team led by John Tauranac with Michael Hertz Associates, and the two sides argued their case in a public debate at Cooper Union in 1978. The question never quite went away: in April 2025 the MTA unveiled its first fully redesigned map since 1979, a diagram with bold straight lines whose designers cited Vignelli's 1972 work as an inspiration.

Reading lines, colours and transfers

Most transit maps share a small vocabulary. Each line or service has a colour, and in some cities a number or letter as well; Tokyo pairs letters with station numbers, while Seoul and Paris number their lines. New York colours its services by the trunk line they share through Manhattan, so the 4, 5 and 6 trains are all green. Where several services share track, they are usually drawn side by side so you can follow each one through the shared section.

Interchange stations get a distinct symbol, often a larger or linked mark, and the line ends are labelled with the terminus names, which is also what the signs on the platform will show as the direction of travel. When planning a trip, read the map in that order: find your line, note the terminus in the direction you want, count the stops and look for the interchange symbol where you need to change. Keep in mind that a diagram can make two stations look far apart when they are a short walk from each other, and the reverse.

How GONOM draws its maps

GONOM's subway maps are not copies of any official map. Each one is drawn by our own code from open station data: station coordinates and the order of stops on each line. The code first projects every station's latitude and longitude onto a flat plane measured in kilometres, centred on the network. It then lays a grid over the city, with a cell size set to a little over half the typical distance between neighbouring stations, and snaps each station to the nearest free point, placing the busiest interchanges first so they stay closest to their true position.

Between two stations the track is drawn octilinearly, Beck's rule of 0, 45 and 90 degrees: a straight run, one diagonal and another straight run, with the bend centred. Where several lines share the same pair of stations, they run as parallel lanes, so in Oslo you can see all five metro lines run side by side through the central tunnel. Unlike Beck, GONOM does not force even spacing, so the map keeps a rough sense of real distance, and a kilometre grid and scale bar stay meaningful.

Interchanges are drawn as rounded squares, termini as squares and other stops as small circles. You can zoom out only as far as the whole network and in to about four times that, and the view always stays over the network. Labels are placed so they never overlap, which means some names appear only as you zoom in. Tap a station for its data sheet, or tap a line in the legend to show it alone.

Maps to explore, and rides to match

GONOM has maps for 35 cities. London is the place to start, with eleven Underground lines on Beck's home ground. New York shows the trunk-line colours, with parallel green, red or yellow lanes where services share track. Paris, with its sixteen lines including 3bis and 7bis, shows how dense a network can get, while Copenhagen, with four lines meeting at Kongens Nytorv, is small enough to take in at a glance.

Two cab-view videos on GONOM pair well with the maps. The BART Yellow Line ride runs from San Francisco airport under the Bay to Antioch, and on the San Francisco map you can follow the same line and see where it shares track with the others. The Yamanote Line video makes a full loop around central Tokyo; it is a JR line rather than part of the Tokyo Metro map, so watching it alongside the map shows how the loop ties the subway lines together at stations such as Shinjuku, Shibuya and Ueno.

Watch these journeys on GONOM

Subway maps mentioned

London · New York · San Francisco Bay Area · Tokyo · Paris · Seoul · Oslo · Copenhagen