Optimizing The Evaluation of The Life Cycle Impacts of Intersection Control Type Selection
Corresponding Author: Joy Davis, Institute for Transportation Research and Education
Presented By: Joy Davis, North Carolina State University
Abstract
Two-way stop controlled (TWSC) intersections can frequently be converted to other facility types to improve safety, operations, and other types of issues. Yet, transportation agencies across the United States have historically lacked standardized guidance for considering the cost effectiveness of various intersection control types over the course of their life cycles. As a result, this research focuses on the development of a new methodology and user-friendly computational tool that can be used in the planning phase of projects involving conversions of TWSC intersections to other intersection types with the goal of optimally allocating public funds. The methodology combines enhanced Highway Capacity Manual methods and standard cost benefit analysis strategies to calculate the long-term net benefits of converting a TWSC intersections to three different intersection alternatives: 1) all-way stop controlled, 2) signalized, and 3) roundabout types. Based on user inputs and standard state and national figures, site-specific construction and maintenance, user delay, and safety costs and benefits are calculated for each of the three conversion types. Similar tools require that users derive data for variables such as delay and safety in a secondary external platform and then manually enter that data into the tool. This multiple platform method can increase room for error and can require significant staff time. Alternatively, the computational tool created through this project requires minimal user inputs and calculates all necessary variables in one platform, which can save staff time and money. As part of this study, new empirically based defaults were developed for many of the variables necessary for this process. Cost and benefit calculations for each alternative are projected into the future using a methodology that considers the changing value of money over time. The resulting dollar figures can be compared to identify the intersection type that offers the greatest return on investment to citizens over a user-specified time period. While this study specifically focused on developing a intersection conversion analysis methodology for North Carolina specifically, the tool is currently being adapted for national use.