The Best Maps We've Seen of Sandy's Transit Outage in New York · 25/01/2013  · When that happened, New Yorker Alastair Coote modified the public GTFS feed from the New York Metropolitan

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EMILY BADGER JAN 25, 2013 2 COMMENTS

MAPS

The Best Maps We've Seen of Sandy'sTransit Outage in New York

By now, tales of Hurricane Sandy’s impact on the New York City transit system have been widely

and well told. The storm managed, with awe-inspiring force, to sever the subway arteries of the

largest city in America. And just as impressively, New York managed to bail out the water and get

moving again.

But we were struck recently by a pair of novel images of the city before and after its transportation

network fell into disarray. These two maps come courtesy of the developers behind

OpenTripPlanner. This first one, showing the city before the storm, illustrates how accessible each

corner of New York was with a typical morning’s use of the transit system:

OpenTripPlanner Analyst project

The yellow areas are the parts of the city that 7.5 million New Yorkers can reach from home in less

than an hour by public transit and walking. The red areas are within an hour’s commute of 6

million people in the metropolitan area. The blue areas are accessible by 4 million people, and the

gray areas by 2 million.

And then there’s this map, which shows the same landscape as it was accessible to New Yorkers

right after Hurricane Sandy:

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OpenTripPlanner Analyst project

To unpack exactly what we’re looking at here – and what these pictures mean for urban planners

elsewhere – it’s helpful to step back a bit. Geographers and planners have talked for decades of

building accessibility measurements to illustrate and understand how far people are located in cities

from the resources they need. But until now, it’s been difficult to paint that picture with any real

fine-grained detail. You may have seen, for instance, more basic maps that illustrate all the jobs or

affordable housing units within a given radius drawn around a metro station.

“You’d see low levels of detail, and big blocks of color,” says Andrew Byrd, one of

OpenTripPlanner's main contributors. He's been trying to re-purpose the tool for transportation

planning and analysis and worked on the above maps. “We’re trying to get very precise, and we’ve

been able to do that by having all this data available that we didn’t have before.”

These two maps were built using Census data and the OpenTripPlanner route-planning tool, a

multi-modal, open-source platform that models travel itineraries for users (with the help of GTFS

data feeds from transit agencies, among other sources). Sandy effectively disabled all of the

underwater subway tunnels connecting Manhattan with other parts of New York, dramatically

altering the transit service for several days. When that happened, New Yorker Alastair Coote

modified the public GTFS feed from the New York Metropolitan Transit Authority to remove the

closed subway stations and account for added shuttle service after the storm. By doing that, he

created an emergency route-planning tool using OpenTripPlanner to help New Yorkers navigate

the city with dramatically reduced transit service.

Byrd had meanwhile been experimenting with OpenTripPlanner as an instrument for urban-

planning analysis. "This was kind of a perfect situation to apply it," he says. Coote's modified GTFS

feeds created an opportunity to map mobility in the city in scenarios with normal and dramatically

altered transit service. You can think of the above images as insanely complex travel-time maps.

Cities previously wrote about travel-time maps like this one, which illustrates how far a person can

travel on transit in 30 minutes from the center of Chicago:

Mapnificent

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Byrd's maps more or less simultaneously illustrate that picture, before and after Sandy, for every

person living in the New York Metropolitan area (based on Census data showing the number of

residents per block throughout the city). “It’s as if everyone in the city took transportation at the

same time to everywhere they could possibility go – at the same time – and then you accumulate

everything,” Byrd explains.

You can also think of the result this way: For each pixel on the above maps, OpenTripPlanner has

calculated how many people in New York are within an hour of there by transit and foot.

Manhattan normally appears as the most accessible place in the city, shown in bright yellow in the

first map. And this is no accident.

“There’s really this incredible connection between how accessible places are, and how densely

populated they are, and densely used and densely built up they are,” Byrd says. You can argue

about whether this correlation happens because transit access enables density, or because transit

follows density where it already exists. “To me the most important thing is not which one causes

the other,” Byrd says. “The most important thing is that public transit networks – the structure

they have, and how they’re connecting things – that completely changes how people perceive

distances.”

In cities, we perceive distance not by miles traveled but by the time required to cover those miles.

And so bright yellow Manhattan feels like the center of New York, even thought it isn’t

geographically in the middle. “It’s the place where the most people are the closest to the most other

people,” Byrd says.

At least, that was the case the day before Sandy.

“Just cutting some of the lines in the transit system completely changes that landscape,” Byrd says.

This third map shows the difference between the above two – in other words, the places where

accessibility was most dramatically impacted by Sandy:

OpenTripPlanner Analyst project

The city has long since returned to normal, to the map shown at the top of this post. But looking

back on these visualizations, two things become clear for New York and any other city moving

forward: Transit access dramatically changes a city's landscape as it's experienced by people moving

through it, and unlikely tools like trip planners may be just what we need to start filling out that

picture.

Keywords: New York, Mobility, Accessibility, OpenTripPlanner, hurricane sandy, Disasters, Transit

Emily Badger is a staff writer at The Atlantic Cities. Her work has previously appeared in Pacific

Standard, GOOD, The Christian Science Monitor, and The New York Times. She lives in the Washington,

D.C. area. All posts »

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