Two-Way Stop Controlled (TWSC) intersections are usually associated with traffic safety or operational concerns as volumes grow. One solution to improve these crossings is to convert the intersection to all-way stop control (AWSC), a roundabout, or a traffic signal. Obviously, each of these control types has unique advantages and disadvantages. In particular, conversion to AWSC addresses the safety issues with minimal construction and maintenance costs; however, with a potentially large increase in delay. Signalization also improves safety and reduces delay to the side street movements; however, it is often associated with significant construction, maintenance, and operational costs. Finally, roundabouts often require significant upfront construction costs; however, they require minimal long term maintenance and operational costs while still significantly improving traffic safety and reducing delay when used correctly.
There is a lack of guidance for considering the cost effectiveness over the life cycle of the installation among various intersection improvement control types. Therefore, life cycle costs are often not the focus of the decision process and might not be considered at all. In fact, it is very common for a TWSC intersection to be converted to an expensive traffic signal; however, many times a more cost effective intersection type could provide the same or better long term benefits if the impacts were considered over the entire life cycle of the intersection. This project will evaluate the costs and benefits associated with the conversion of a TWSC intersection to each of these alternative intersection control types. A simple computational engine will be developed for NCDOT where users enter variables such as lane geometry and traffic volume at a TWSC intersection and the engine returns the total life-cycle costs associated with converting the control type to AWSC, signal-controlled, and a roundabout. This tool, at a minimum should take into account costs associated with construction, maintenance, and annual operation, as well as, benefits through user impacts, such as delay and safety.
