Mathematical Models for Predicting Roadway-Characteristics-and-Level-of-Service-Dependent Travel Times on Rural Roads in Thailand

Abstract—With the use of traffic simulation models, travel times on urban streets and highways where average speed primarily depends on traffic volume which is apparently high most of the time, can be obtained. However, on rural roads, especially in Thailand, where congestion rarely occurs due mainly to very low traffic volume, travel time is rather dependent on roadway characteristics and environment than traffic flow. As a result, the traffic simulation models currently available cannot be used to predict the travel times on rural roads in Thailand effectively. This research therefore identifies roadway characteristics and environment affecting speeds of vehicles on rural roads, and subsequently develops the mathematical models based upon road characteristics and environment identified, for predicting travel times of passenger and freight transport on rural roads in Thailand, by using multiple linear regression. Data on roadway characteristics and travel times, used to calibrate the mathematical models, were collected onsite from 66 rural roads in Thailand and more than 20,000 vehicles, respectively. The research reveals that speeds and travel times for both passenger and freight transportation on rural roads in Thailand appear to be mainly influenced by adjacent land use, presence of horizontal curvature and bridges along the road. However, the effects of these factors are found to vary according to level of service for the roads.