Image from Transport for London.

Maps matter. Metro’s and London’s transit maps present distorted geographies in order to make the system’s organization clearer. They have become iconic, but the way they present distances shapes people’s understanding of space and distance in their region.

An NYU study found that distances on such maps affect people’s travel choices much more than actual distances. Riders on the London Tube who had choices between multiple transfers were twice as likely to take the route that was shorter on the map but longer in real life. Even people who ride every weekday did this.

This reinforces an important idea we’ve discussed before: The map forms people’s views of a city. To many people, the Metro map is the mental image of DC and the surrounding area. Geographic distortions may be appropriate to help a map be simpler, but designers should consider carefully the effect of each such change.

Peter Dunn pointed us to a Metro map he made, which makes distances match travel times. The overall shape of the map is the same, but stations that take longer to travel between appear farther apart:

Map by Peter Dunn.

This is less useful in many ways than the classic map. Most riders travel to and from stations in the core, and tourists or other riders unfamiliar with the system are most likely of all to do so. This map gives little space to that area and leaves large amounts of empty space at the edges.

However, based on the NYU study, this map would leave people with a much more accurate conception of the region. The question for mapmakers is, when is it more valuable to make a schematic map simple and understandable, and when does the way it distorts people’s own mental maps of the area outweigh the benefit?

The current map, for example, greatly distorts the distances between stations and the key attractions on the Mall, which are most relevant to tourists and visitors. Someone looking at the map would think Metro Center and Federal Triangle are a lot closer to the White House than McPherson Square and Farragut West, which is not the case. Union Station appears to be much farther from the Capitol than it is; on the map, it looks like it’s the same distance as Potomac Avenue.

Metro plans to add more rush hour trains over the Yellow Line bridge and have fewer rush hour trains going past Arlington Cemetery. People who ride from Franconia-Springfield to Foggy Bottom don’t like that their commutes will get longer. But as Matt showed, the time difference is pretty small.

Would a map like Dunn’s make this clearer, since it’s obvious that the trip from Franconia to Pentagon is far longer than the trip either way into DC? Would that affect rider support for the plan? In this case, it may not matter, since Metro is going ahead regardless, but many future and more political decisions may well turn on people’s mental maps, accurate or not.

David Alpert is Founder and President of Greater Greater Washington and Executive Director of DC Sustainable Transportation (DCST). He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle. Unless otherwise noted, opinions in his GGWash posts are his and not the official views of GGWash or DCST.