Abstract
Crashes at isolated rural intersections, particularly those involving vehicles traveling perpendicularly to each other, are especially dangerous due to the high speeds involved. Consequently, transportation agencies are interested in reducing the occurrence of this crash type. Many engineering treatments exist to improve safety at isolated, high-speed, signalized intersections. Intuitively, it is critical to know which safety treatments are the most effective for a given set of selection criteria at a particular intersection. Without a well-defined decision making methodology, it is difficult to decide which safety countermeasure, or set of countermeasures, is the best option. Additionally, because of the large number of possible intersection configurations, traffic volumes, and vehicle types, it would be impossible to develop a set of guidelines that could be applied to all signalized intersections. Therefore, a methodology was developed in in this paper whereby common countermeasures could be modeled and analyzed prior to being implemented in the field. Due to the dynamic and stochastic nature of the problem, the choice was made to employ microsimulation tools, such as VISSIM, to analyze the studied countermeasures. A calibrated and validated microsimulation model of a signalized intersection was used to model two common safety countermeasures. The methodology was demonstrated on a test site located just outside of Lincoln, Nebraska. The model was calibrated to the distribution of observed speeds collected at the test site. It was concluded that the methodology could be used for the preliminary analysis of safety treatments based on select safety and operational measures of effectiveness.
Highlights
In recent years, many transportation agencies have considered implementing safety treatments at high speed, isolated intersections
The two treatments examined were an Advance Detection System and an Advance Warning System; these treatments were compared to the “do-nothing,” or, no safety treatment scenario
Conclusions of the proposed methodology - The methodology described in this paper was an effective tool for the analysis of engineering safety treatments because it takes into account the stochastic nature of traffic and allows for the testing of various measures of effectiveness that would be difficult, if not impossible, to conduct using standard analytical models
Summary
Many transportation agencies have considered implementing safety treatments at high speed, isolated intersections. Traffic agencies must examine each intersection with respect to its specific characteristics To address this issue, the current paper describes a methodology for analyzing the safety and efficiency metrics associated with various safety countermeasures at a particular intersection. An agency could not implement an Advance Warning System (AWS) at a site and turn it on and off to analyze critical safety measures of effectiveness (e.g., crash rates). In this situation, the only option is to either examine the success of countermeasures at other sites, model the different countermeasures, or some combination of these two approaches. Rilett Development of a statistically-based methodology for analyzing automatic safety treatments
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