RACHEL MARTIN, HOST:
The good people of Boston have just voted, not to elect anybody. But they have voted to choose a new subway map. The contest closed on Friday. Washington, D.C. also released a new metro map this month.
Psychologist Max Roberts studies subway maps and has come to tell us what makes a good one. He teaches at the University of Essex. He joins us from the BBC in London. Thanks so much for being with us.
MAX ROBERTS: Oh, hello.
MARTIN: So what is the key to making a really good subway map?
ROBERTS: There's a lot of things you have to balance at once and different people balance different things. But what I'm looking for in good design are five different things. I'm looking for simplicity of the line trajectories. So, you know, the line should be straight, not zigzagged.
Next, I'm looking for something called coherence. Like, coherence is more subtle. It's about the overall shape and organization of a map. So, you have things like lines parallel, line symmetrical with each other. That's much more subtle, yet it makes the difference between a good map and a great map.
I'm looking for balance so I don't want crushed-up stations in one part of the map, empty space in another. And something called harmony. Harmony is about sort of the elements of a map that people find it like likable. So things like lines crossing at 90 degrees is likable, equilateral triangles. And finally, you've got to achieve all those without distorting the geography too much.
MARTIN: Boston asked the public to help select its next subway map. Is that a good idea?
ROBERTS: It's a very, very bad idea.
ROBERTS: In our research, we test map usability by giving people objective tasks to do. We asked them to find stations. We asked them to plan journeys. We see how long they took it. We see what sorts of journeys they planned. And from that we can tell whether the map is working effectively or not. We also asked people which maps they prefer. And what we find is there is zero correlation between the objective usability measures and whether people like a map or not.
MARTIN: Are colors helpful?
ROBERTS: They're differently helpful. The trouble is, as networks get complicated, they run out of colors. And some networks are over colored, as well. And famously, the Vignelli 1972 New York subway map had one color for each individual line. And they were random sort of colors, as well. So you had sort of incredible stripy maps in which the colors were really sort of just overwhelming the user, completely unable to work out what the actual structure of the one of each network was.
MARTIN: Is there a city that has just really figured out how to do this?
ROBERTS: Well, no.
ROBERTS: The trouble is I've been doing this for too long and I keep finding things - faults in everything. I've never seen a map I haven't wanted to fix and that includes my own designs.
ROBERTS: The London map is very popular but it's really sort of well past its sell-by date. It's a very tired, old design that can't cope with a hundred extra stations on it, compared with 1933, but the same size piece of paper.
MARTIN: As someone who has studied these maps and sees all these errors all the time, it must be particularly frustrating for you when you see a subway map become a kind of cultural icon - like the London tube or the subway in New York. Does that irk you when you see that because you see all the errors?
ROBERTS: It doesn't, especially if the map is very powerful. And, you know, people can like all sorts of maps and people differ in the maps they like. If all the subway maps in the world were perfect, then I'll be out of a job.
MARTIN: Well, there is that. Psychologist Max Roberts talking to us about what makes for the perfect city subway map. Thank you so much for talking with us, Professor.
ROBERTS: Thank you for inviting me. Transcript provided by NPR, Copyright NPR.