  Pedestrians and cyclists are vulnerable road users. They are at greater risk
for being killed in a crash than other road users. The percentage of fatal
crashes that involve a pedestrian or cyclist is higher than the overall
percentage of total trips taken by both modes. Because of this risk, finding
ways to minimize problematic street environments is critical. Understanding
traffic safety spatial patterns and identifying dangerous locations with
significantly high crash risks for pedestrians and cyclists is essential in
order to design possible countermeasures to improve road safety. This research
develops two indicators for examining spatial correlation patterns between
elements of the built environment (intersections) and crashes (pedestrian- or
cyclist-involved). The global colocation quotient detects the overall
connection in an area while the local colocation quotient identifies the
locations of high-risk intersections. To illustrate our approach, we applied
the methods to inspect the colocation patterns between pedestrian- or
cyclist-vehicle crashes and intersections in Houston, Texas and we identified
among many intersections the ones that significantly attract crashes. We also
scrutinized those intersections, discussed possible attributes leading to high
colocation of crashes and proposed corresponding countermeasures.
