2000115-Strengthening-Communities-with-Neighborhood-Data

Advances in Analytic Methods for Neighborhood Data 299
it is considered walkable, but this distance may be more or less appropriate
depending on public transit routes, land use, and pedestrian streets,
which were not taken into account in this study.
GIS tools can also be used to craft measures of proximity to disamenities.
Exposure to hazardous wastes was examined from a spatial perspective
for neighborhoods in Detroit (Downey 2006). GIS tools were
used to calculate exposure to toxic releases for each census tract so that
census variables could also be used in the study. Data on the locations and
amounts of toxic releases were obtained from the Environmental Protection
Agency’s Toxic Release Inventory. In order to convert these pointlevel
release data into exposure measures for census tracts, a raster grid
was overlaid on the census tract map. For each cell in the grid, the total
number of pounds of pollutants emitted within one-quarter kilometer
was calculated. The emission score for each tract was calculated by summing
the emissions for the cells in the tract and dividing by the number of
tracts. This procedure can be seen as standardizing the emissions for tract
size and capturing emissions that are adjacent to the tracts themselves.
A study in New York City included a spatial measure of disamenities
that were thought to interfere with park use (Weiss et al. 2011). Because
one of the possible factors was violent crime, several years of point data
on homicides were obtained from public sources. Homicides are relatively
rare events, but they have the potential to induce fear among residents
at both the site of occurrence and over time and space. To quantify
this pattern of influence for the neighborhoods surrounding parks, the
researchers used GIS tools to estimate a spatially smoothed kernel density
grid by using inverse distance weighting from the homicide points.
An average homicide density was calculated for each neighborhood. The
same technique was used to quantify the density of other disamenities,
such as traffic accidents. Disamenities were found to be more of a limiting
factor for park access in neighborhoods with low socioeconomic
status than in more affluent areas.
The above examples demonstrate how GIS tools can be used to craft
measures of neighborhood access and exposure that are more precise
than simple counts of what is present within neighborhood boundaries.
However, many questions remain about the most appropriate buffer
sizes and distance decay functions for particular phenomena. The field
will benefit from continued research that provides empirical evidence to
guide the proper specification of the correct geographic range and scale
for the various processes of interest.