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Could a subtle tweak to Metro’s map fix overcrowding on the Blue Line?

Zhan Guo believes that a change to the Metro subway map could help tackle a historic problem: Northern Virginia commuters who resists switching from the overcrowded Blue Line to the roomier Yellow Line because they prefer a one-seat ride into downtown D.C. (Source: Zhan Guo/NYU)

With Metro’s most recent SafeTrack shutdown, Northern Virginia riders are finally doing the thing that Metro has been asking them to do for years: They’re switching from the historically overcrowded Blue Line to roomier Yellow Line trains.

But after Surge 12 concludes Tuesday, will these riders stick with their new commuting routes?

Zhan Guo thinks he can help. Guo is director of the urban planning program at New York University’s Wagner School of Public Service, and he’s done research into how a simple thing like the design of a subway map can radically shape people’s commuting decisions.

Some of his research has focused on Metro, and he thinks that some of the subway’s overcrowding issues — particularly when it comes to trains going through the bottle-necked Rosslyn Tunnel — could be alleviated, at least in part, by a few subtle tweaks to the map that’s used on trains, in stations, and on phone apps.

For SafeTrack Surge No. 12, the Blue Line takes a hiatus through the end of February

The Blue Line has always been more crowded than the Yellow, due at least in part because many people prefer a one-seat ride on the Blue Line than the prospect of changing trains at L’Enfant Plaza or Gallery Place.

And those rider preferences have become increasingly problematic with Silver Line service adding to the congestion in the Rosslyn tunnel. That’s what prompted the start of Yellow “Rush Plus” service in 2012: “More Yellow, less Blue,” Metro spokesman Dan Stessel said in 2014. “Maximize the space on the river bridge. There’s space available on the bridge. But there’s no more room in the tunnel.”

Guo’s experiments suggest that Metro riders — even longtime ones who are well-acquainted with the system — may alter their commuting patterns because of a tiny change to the map. And the split between the Blue Line and the Yellow Line as it forks in Northern Virginia is a perfect example of the potential for rider reallocation, he says.

Sept. 2012: Metro offering vouchers to transfer from Blue to Yellow line at select stations

To shore up his theory about the power of map design, Guo created a series of tests that he posted on a crowd-sourcing website, enlisting thousands of random test-takers from all over the country, including many in the greater D.C. region.

In the test, Guo showed respondents several pairs of points on a Metro map — Braddock Road and Judiciary Square stations, for example — and then offered two possible routes that they could take to travel between the two stations. He asked the respondents to pick which route they preferred.

But here’s where Guo mixed things up: Some respondents received the standard Metro map that we all see today. Others viewed maps with slight tweaks: the Blue Line was drawn to be slightly longer or more angular, or the Yellow Line showed a smoother and more direct line between Pentagon and L’Enfant Plaza.

The results were significant.

Three different maps showed the Blue Line to be more out-of-the-way as it crossed the Rosslyn tunnel: that section of the route appeared more angular or boxy, but the line was the same length as in the original map. In those cases, the percent of people who opted to use the Yellow Line route increased by sizable amounts: from as little as 1.9 percent, to as much as 5.7 percent.

In another map, he redrew the Yellow Line to be less angular, more of a straight shot between Pentagon and L’Enfant Plaza stations. That also had an effect, encouraging 2.6 percent more people to use the Yellow Line.

“Distance matters, but the shape also matters — and sometimes matters even more than distance,” Guo said.

And in one particularly distorted map — the Blue Line was shown to be longer and a far more circuitous route — the difference was a whopping 9.5 percent of riders who decided to use the Yellow Line instead.

“That map would never happen in reality,” Guo said. “The designers would never allow us to change the map into such an ugly map!”

The results held up even for people who were likely to be well-acquainted with the Metro system, because they listed their zip code in the Washington area and reported that they used public transportation frequently. Guo has done similar research on the London subway network, testing to see the “elasticity” of riders’ choices based on their experience with the system.

In that earlier study, he measured the comparative importance between the map and riders’ experiences when making commuting decisions. For first-time riders, the “elasticity factor” was 2.14 — the map was more than twice as important than the real distance in terms of how they planned their routes. But even for experienced riders, the “elasticity factor” was 1.69, meaning that London Tube aficionados still relied heavily on their subway maps, despite the fact that they had plenty of first-hand experience with the actual time and distance between stations.

“The conclusion is that people trust the map more than their experiences,” Guo said. “Even for people who have used the system for many years, the map still matters.”

Guo said he thinks Metro should consider these subtle tweaks next time they’re updating the map, thinking about current ridership patterns and how they can entice riders to find alternate routes more attractive so they naturally redistribute themselves more evenly throughout the system.

Some might call that practice manipulative. But Guo pointed out that a subway map is always a form of manipulation, rarely ever depicting the geographic realities of where stations and rail routes are located. This, by the way, is the Metro map to geographic scale:

When faced with the honest-to-gosh depiction of the Metro system, people are 13.9 percent less likely to use the Yellow Line than when they view the current map.

“Geographic representation is probably the least important thing to passengers looking at a subway map,” Guo said. “What they want is, number one, a clear depiction of the system. That’s the one big criteria. And number two, they want information presented in the map that would help them find the best route and the shortest path to minimize time.”

Overcrowding in the Rosslyn Tunnel is often a catalyst for delays. Wouldn’t riders want to be subconsciously steered away from the route with the higher propensity for unexpected disruptions and slowdowns?

“You can call it influencing, or manipulating, or misguiding,” Guo added. “But riders don’t care if it’s a distortion of reality or not, as long as the change gets them to their destination more conveniently and quickly.”

SafeTrack closures: These D.C. Metro lines and stations will be disrupted in the next year