An Examination of the Safety of Signalized Intersections in Consideration of Nearby Access Points

Abstract

Effective access management is critical to the safe and efficient operation of roadway corridors. Access management is particularly important near signalized intersections, where adjacent driveways exacerbate the crash risks created by conflict points at the primary intersection. This study examines the relationship between crash risk and access spacing in the vicinity of 415 signalized urban intersections. The frequency of access points near each signalized intersection of interest was collected to examine the differences in experienced crash frequency over a five-year period. Additional information about each access point was collected, including details of turning movement restrictions and estimated driveway volumes. A series of buffers of varying radii were considered to examine how crash rates varied based upon the spatial proximity of access points to each signalized intersection. In addition, traffic volume and roadway geometric information was collected and utilized as a part of this evaluation. A series of crash prediction models were estimated to discern how crash rates varied based upon the access point density on the intersection approaches along the major (i.e., higher volume) roadway. As the number of access points increased, the crash rates also increased. This relationship was consistent in direction, but varied in magnitude, depending on the size of the buffers, which varied in radius from 50 ft to 600 ft at 50-ft intervals. The number of crashes by location was also shown to vary based upon the number of travel lanes, the number of intersection legs, and the land use type of the adjacent driveways.

Safety Evaluation of Freeway Exit Ramps with Advisory Speed Reductions

“…Crashes are known to be random, discrete, and non-negative integers. Two types of regression model are frequently used to develop SPFs based on prior studies: Poisson ( 26 ) and negative binomial (NB) models ( 26 – 28 ). Under the Poisson model, the probability of exit ramp i experiencing y i crashes during a specific time period can be calculated using Equation 1.…”

Use of Real-Time Traffic and Signal Timing Data in Modeling Occupant Injury Severity at Signalized Intersections

“…Several studies have focused on real-time safety analysis on arterials with signalized intersections (3,5,11,30,31). The real-time traffic data from these studies were collected using different approaches, including video recording, Bluetooth detectors, and inductive loop detectors.…”

“…A buffer of 300 ft was specified in ArcGIS software at each signalized intersection in the study corridor to identify all intersection-related crashes. Literature indicates that intersection influences on traffic crashes extend from 200 ft to 300 ft (30). Several other studies have adopted this threshold to define the crashes at intersections for safety analysis (31,32).…”