How Does Foot Traffic Correlate With 311 Reports in NYC?

‘Eyes on the street’: 311 and the sidewalk ballet
by Melissa Sands

The sidewalks of New York City were a favorite subject of writer and activist Jane Jacobs.  In The Death and Life of Great American Cities (1961), she described the city as an “intricate ballet” of movement and change that plays out on the sidewalk “…bringing with it a constant succession of eyes.” Jacobs believed that “eyes upon the street”—by which she meant the watchful gaze of neighborhood shop-owners and residents, alert to minor disturbances and problems—are essential to a vibrant, safe city.

Map by Pitch Interactive from 2010 where blue represents the fewest 311 complaints and red the most.

In 2003, the city’s “eyes” gained a direct link to city government with the launch of NYC 311, NYC’s non-emergency customer service line. NYC’s 311 line operates 24/7 and assists 60,000 callers per day. Residents and visitors report everything from noise complaints to broken parking meters to rodent sightings. Those who contact 311 are sentinels of the sidewalk, supplying vital information about what’s happening on the ground to the city agencies responsible for fixing problems.

Does higher foot traffic, and therefore more ‘eyes on the street’, translate into more 311 reports?

A high density of pedestrians means greater potential for complaints about a blocked sidewalk, an overgrown tree branch, or an overflowing litter basket, but what does this mean for 311?  Armed with data from Placemeter, which measures activity on streets and sidewalks from a network of sensors, and NYC OpenData, I set out to study how rates of pedestrian traffic dictate what gets reported to 311.

First I combined NYC 311 reports with Placemeter-generated foot traffic data from over the course of two weeks last summer. Restricting the analysis to data-rich Midtown Manhattan, I spatially interpolated hourly daytime foot traffic for every inch of Midtown. On top of the foot traffic layer, I then overlaid NYC 311 data from NYC OpenData for the same period and extracted predicted values of hourly foot traffic for each geocoded 311 report. In other words, each 311 call is linked with how many pedestrians, on average, were in the vicinity of the problem when it was reported to the City.

On this map of midtown Manhattan, each dot corresponds to a 311 report pertaining to an issue occurring outdoors—on a sidewalk, street, park or playground—during last two weeks of June, 2014. The colors of the dots correspond to the average amount of foot traffic, measured in people per hour, at the location of the 311 report.

The first take-away is that, indeed, more people means more ‘eyes on the street’, but only up to a point: when foot traffic is at its highest, 311 reporting tends to drop off. One possible explanation is that who is on the street matters; highly trafficked areas are often those that swarm with tourists, who would be less likely than residents to report problems to 311. Another potential explanation is the bystander effect, a social psychological phenomenon in which the presence of many other individuals decreases the chances that any one person will report a problem.

The second take-away is that the relationship between foot traffic and 311 reporting varies by the type of complaint. For certain categories of 311 complaints, the number of calls is relatively unaffected by the quantity of foot traffic. For example, in Midtown complaints about sidewalk condition are generated at a similar rate regardless of how many people are around.

This plot shows the relationship between hourly foot traffic and various types of 311 complaints in midtown for June 17-30, 2014. The colored lines represent the difference between foot traffic density and 311 call density for different types of call. If a call type occurred uniformly across the city (i.e., if there is no relationship between foot traffic and call frequency), then the colored line would trace the dotted gray horizontal line at zero. Instead we see that, for example, noise complaints (in red) occur less than expected in high-traffic areas.

Calls regarding air quality spike around 800 pedestrians per hour but quickly fall off in areas of middle to high foot traffic. Street noise, one of the city’s most commonly-reported grievances, peaks around 1,200 pedestrians per hour but is rarely reported at more bustling midtown locations. This may reflect expectations about where noise is acceptable, e.g., we expect Times Square to be loud but are less tolerant of the urban cacophony when it resonates on a residential block.

Meanwhile, reports of homeless persons in need of assistance are rarely made in the least trafficked areas but are over-represented in places with a high density of foot traffic.

Nearly a half century after Jacobs coined the term ‘eyes on the street’, the combination of Placemeter and 311 data allows us to explore the nuances of an idea that has influenced urban planners around the world.  These novel data sources can breathe new life into Jacobs’ ideas about the vitality of the city and its sidewalks. They can help us to better understand how pedestrians engage with their city and its intricate sidewalk ballet.

Melissa Sands is a PhD Candidate in Government at Harvard University

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