It has been suggested that GPS monitoring data can be used to estimate distances traveled and speeds of travel during active and non-active travel journeys and, that when combined with accelerometer monitoring, GPS data can be used to identify travel mode. We tested whether the distances between successively captured GPS way points can be used to measure distances walked in varying environments in NYC. Students walked a series of structured routes in areas with high and low building bulk density and on streets with high and low tree canopy cover while wearing GPS monitors. The sums of distances between successive GPS way points over estimated travel distances and over estimates were larger in areas with high building bulk density and on streets with high tree canopy cover. Algorithms using distances between successive GPS points to infer speed or travel mode may misclassify trips differentially across built environment contexts. The abstract can be found HERE and the full paper will be available in the American Journal of Public Health.
Below is an image of the GPS data collected during walks along streets in low and high building bulk density.
GPS data collected during walks along streets in areas with low (left side) and high (right side) building bulk density. Image by Dan Sheehan.
The Journal of Maps recently published our article showing a high resolution map of neighborhood physical disorder in New York City.
Physical disorder – the deterioration of urban spaces owing to social forces favoring neglect and abandonment – has long been of interest to social scientists [1, 2]. Criminologists and sociologists have debated the controversial ‘broken windows’ theory that disorder encourages violent crime [3, 4]. Separately, psychologists and psychiatric epidemiologists have investigated whether living amidst disorder negatively affects mental health, not only directly as stress induced by encountering a chaotic environment triggers earlier cognitive decline  but also indirectly as residents adopt coping mechanisms such as alcohol use that themselves trigger longer-term harms .
The data underlying the map was collected using neighborhood audits implemented via Street View. In addition to data collection in NYC, the team collected neighborhood physical disorder data from San Jose, California; Detroit, Michigan; and Philadelphia, Pennsylvania. Below is a heat map of Philadelphia showing the distribution of neighborhood physical disorder across the city.
Neighborhood physical disorder in Philadelphia. Draker area within Philadelphia have higher levels of physical disorder.
The Mailman School blog reached out to Steve Mooney to discuss our research on pedestrian injuries. The post shows a series of Street Views of the key features that were associated with injuries. The article is Here. And an article in New Scientist. And on Forbes.com.
Street Viewing 125th Street
In 2013, an estimated 70 000 pedestrians were injured or killed by motor vehicles in the United States. In New York City more pedestrians than vehicle occupants have been killed by motor vehicles each year since at least 1910. Pedestrian safety is not only vital for public health directly through reduced traffic-related morbidity and mortality, but also indirectly as the perception of increased safety from traffic encourages outdoor physical activity, with consequent mental and physical health benefits.
We just published an article in the American Journal of Public Health in which we use Google Street View to identify characteristics of streets and intersections associated with pedestrian injuries and fatalities. Following up on our work using Street View to conduct virtual street audits (1, 2, 3), we used the CANVAS system to collect data on built environment characteristics at street intersections with varying numbers of pedestrian injuries. Higher counts of pedestrian injuries at intersections were associated with the presence of nearby billboards and bus-stops. Injury incidence per pedestrian was lower at intersections with higher estimated pedestrian volumes.
The use of virtual street audits allowed us to complete the research in a much shorter time period than comparable studies that use in-person audits to collect data at intersections. We are planning to expand this research to conduct a nationwide study of built environment risk factors for pedestrian injury.
Jerome Ave and Fordham Road in the Bronx, the intersection with the highest number of injuries in our study.
We just published a paper in the American Journal of Preventive Medicine showing that differences in residential neighborhood walkability in New York City (NYC) are associated with how residents utilize neighborhood space and are associated with total weekly physical activity. Higher neighborhood walkability was associated with significantly more physical activity and differences in activity attributable to variation in urban design were substantial when compared to the recommended goal of achieving 150 minutes of moderate intensity physical activity per week.
Examples of high and low walkability neighborhoods and a map of neighborhood walkability for all of NYC
The research was conducted in collaboration with researchers from the NYC Department of Health and Mental Hygiene and analyzed Global Positioning System (GPS) and physical activity data from the Physical Activity and Transit Survey (PAT). For a period of a week, PAT study participants wore an accelerometer to continuously measure physical activity and a GPS logger that recorded the participant’s location multiple times per minute. In all, the PAT Survey collected over 8 million GPS location readings, known as waypoints, as the study participants (n=803) went about their daily lives.
Four illustrative examples showing how GPS logging data can be used to characterize which parts, and how much, of someone’s residential neighborhood is actually utilized by the person. The circle represents all neighborhood space within 1Km of a residence and the white area reflects a minimal convex polygon that encompasses GPS waypoints. They grey area represents space within 1Km of the residence that was not utilized.
To identify how much area within their residential neighborhood participants utilized during the monitoring period, we defined a minimally convex polygon around GPS waypoints falling within 1Km of each participant’s home. This 1Km circular area around the home has commonly been used in prior research to define study participant’s residential neighborhoods. The use of convex polygons around GPS waypoints to define the utilized residential area is similar to methods used in wildlife studies to define the home territory of animals. In NYC we see that residents vary considerably in how much of the total 1Km circular residential neighborhood area they actually use as judged by the area encompassed by the GPS data. Continue reading
Viewing 125th Street
The Centers for Disease Control and Prevention and Department of Transportation just released the new Transportation and Health Tool, which provides easy access to data that examines the health impacts of transportation systems. The Transportation and Health Tool provides data on 14 transportation and public health indicators for each state, metropolitan statistical area (MSA), and urbanized area (UZA). The indicators measure how the transportation environment affects health with respect to safety, active transportation, air quality, and connectivity to destinations. You can use the tool to quickly see how a state, MSA, or UZA compares with others in addressing key transportation and health issues. The tool also provides information and resources to help agencies better understand the links between transportation and health and to identify strategies to improve public health through transportation planning and policy
Jarlath O’Neil-Dunne at the University of Vermont just announced the release of a statewide, high-resolution tree canopy dataset for Pennsylvania. The resolution of the data is 1 m which makes it 900 times more detailed than the National Land Cover Dataset; this is an amazing feat.
We previously worked with Jarlath to create tree canopy data for NYC and looked at the link between tree canopy coverage and asthma and allergic sensitization among children in NYC.
Tree canopy coverage in Washington Heights, NYC
Analyses of place and health have been largely cross-sectional, and new challenges are faced as we wrangle longitudinal geographic data. Our group just published a manuscript detailing our work to clean and code data on all NYC metropolitan area businesses over the period 1990-2010. Our goal was to use twenty years of business establishment data to characterize changes in neighborhoods in terms of the retail food environment, access to physical activity venues, access to medical facilities and access to other commercial and not-for-profit establishments.
Our process included re-geocoding 3,161,715 business locations to avoid disproportionately missing data on older businesses; identifying and coding health-relevant businesses such as food sources and fitness venues across the years; and collapsing potential duplicate business records by location, year, and business category. Spot-checking was used, and the data are set up to allow for sensitivity analyses to check the robustness to these decisions as we move forward.
This effort was championed by lead author Tanya Kaufman, who has engaged in this effort since her MPH practicum project using these data. Daniel Sheehan was the lead geographer on the project and developed the re-geocoding strategies and created time-lapse visualizations of businesses entering and existing the environment. One of Dan’s visualizations can be seen here. It shows the location of Healthy Food Outlets from 1990 to 2010.
The focus of this project was not only to understand and improve the quality of data for future analysis, but also to develop scalable approaches that can be used with the larger national dataset. We have recently been funded to purchase the nationwide business establishment data and to link these data to ongoing cohort studies of cardiovascular disease (R01AG049970-01A1, PI: Lovasi).
Viewing 125th Street
The CDC released a new direct systematic observation data collection instrument for measuring the core features and quality of the built environment related to behaviors that affect health, especially behaviors such as walking, biking, and other types of physical activity. The core features assessed in the BE Tool include: built environment infrastructure (e.g., road type, curb cuts/ramps, intersections/crosswalks, traffic control, transportation), walkability (e.g. sidewalk/path features, walking safety, aesthetics & amenities), bikeability (e.g., bicycle lane/path features), recreational sites and structures, and the food environment (e.g., access to grocery stores, convenience stores, farmers markets, etc.).
Get the tool [HERE]
Trail map for Fort Tryon Park
Providing neighborhood access to clean, safe and engaging park spaces is a strategy being adopted by many communities to promote physical activity. We just published a systematic review of the literature assessing the link between park access and physical activity. After screening 10,949 abstracts that met the search criteria of 1) published between January 1990 and June 2013; 2) US-based with a sample size greater than 100 individuals; 3) included built environment measures related to parks or trails; and 4) included objectively measured physical activity as an outcome, 20 research studies were identified for review.
Five articles reported a significant positive association between parks and physical activity. Nine studies found no association, and six studies had mixed findings. Studies that used study subject’s self-reported (vs. independently-measured) measures of neighborhood park environment characteristics and smaller (vs. larger) neighborhood definitions were more likely to find positive associations. We recommend strategies for further research, employing standardized reporting and innovative study designs to better understand the relationship of parks and physical activity.