Analyzing Characteristics of the Unreliable Segments of the National Highway System across South Eastern States of the United States

Abstract

The latest transportation law in the United States continues to put emphasis on a performance management approach similar to the previous one. Since the transportation performance management rules were made in 2017, limited work has been done to understand the travel time reliability on the national highway system (NHS) and the factors influencing it. This study contributes to the literature by analyzing the characteristics of the unreliable segments of the NHS in 13 south eastern states. It was observed that there was a higher percentage of unreliable segments in the non-Interstate NHS (about 34%) than in the Interstate system (about 13% of segments were unreliable). Analyses of the unreliability of the Interstate and non-Interstate NHS were conducted separately to understand each of them better. To capture the influence of the attributes on the reliability of the NHS segments, multivariate binary logistic models were developed. The results from the models suggest that the reference traffic message channels (TMCs), which were characterized by being in urban areas with shorter length (≤0.25 mi) and ≤10% trucks in the traffic stream, generally have a higher chance of being unreliable than those that are not in the reference category. Interstate TMCs on bridges, tunnels, or causeways, and those with directional traffic volume greater than 30,000, have higher chances of being unreliable than the reference category. The chances of internal TMCs (between decision points) in the non-Interstate NHS being unreliable were about 14% higher than the mean chance of the reference TMCs.