Research | 2014

Influence of Road Cross Section on Access Spacing

  • Authored by:  Dr. Karen Dixon , Dr. James L. Gattis , Yanfen Zhou

This report presents a study on the influences of select cross-sectional-related design elements (specifically median configurations and bicycle 
lanes) and their impact on crash severity and type, as well as the associated driver gap acceptance for turning maneuvers at midblock driveway 
locations on urban arterials. The primary goal of this proposed research is to better understand how the median and bicycle lane configurations 
can influence safety and operations at driveway locations.

The research team utilized crash data, traffic data, and roadway information from driveway locations in the U.S. states of Oregon, Arkansas and 
Oklahoma. The project team supplemented the data with digital videos acquired during field studies of the sites. The traffic videos helped the 
research team better understand how road features and traffic influenced driver behavior at selected urban arterial driveway locations. As part of 
this effort, the research team conducted gap-acceptance studies to determine the critical gaps for driveway locations at arterial roads with and 
without bicycle lanes. The research team evaluated four different critical gap analysis methods to estimate the driveway operations and noted 
potential procedural biases associated with two of the techniques. The report describes these field studies and summarizes how the gap 
acceptance varied at the different arterial driveway locations. The research team also performed simulation analysis in CORSIM in order to 
examine the influence that median type, traffic volume, and access density have on traffic operational performance.

Access Spacing, Auxiliary Lanes, Driveways