Access Management Techniques to Improve Traffic Operations and Safety: A Case Study of a Full vs. Directional Median Opening

Access management applications, which could effectively be used to improve traffic operations and safety, are getting increased popularity. While there are some studies providing important information on various access management methods and techniques, questions still remain surrounding the effects of specific access management treatments on roadway operations and safety. This study provides the results of a case study in one of such areas, where the operational and safety characteristics of a full median opening are compared with those of a directional median opening, in the form of a before-and-after study. Field data were collected at the site by using video camera technique. Before period consisted of one week of field data where the intersection operated as a full median opening. The median was then converted into a directional median opening by using temporary physical barriers and field data were collected again in the same way for another week. Only the data collected during daytime, under good weather conditions with no special events were considered in the analysis. Operational characteristics were measured in terms of weighted average delay and weighted average travel time experienced by the left turning vehicles from the stop controlled approach (driveway), where safety performance was measured in terms of number of conflicts and rate of conflicts. According to the findings, the total weighted average travel delay was significantly reduced after the median opening was made to function as directional. However, changes in the travel times were not statistically significant. The average number of conflicts per hour was reduced by almost 50 percent whereas conflict rate per thousand involved vehicles was also significantly reduced. Additionally, the severity of conflicts measured subjectively was also found to be reduced during the after time period. Accordingly, both traffic operations and safety situations were found to be improved when the full median opening was converted to a directional opening.