Browsing by Subject "Value of Time"
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Item Empirical Measurements of Travelers' Value of Travel Time Reliability(2014-08-12) Danda, Santosh RaoTravel time and travel time reliability are two fundamental factors influencing travel behavior and demand. The concept of the value of time (VOT) has been extensively studied, and estimates of VOT have been obtained from surveys and empirical data. On the other hand, although the importance of value of reliability (VOR) is appreciated, research related to VOR is still in its early stages. VORs have been estimated using surveys but has almost never estimated using empirical data. This research used empirical data to take an initial step toward understanding the importance of travel time reliability. Katy Freeway travelers face a daily choice between reliable tolled lanes and less reliable but untolled lanes. An extensive dataset of Katy Freeway travel was used to examine the influence of time, reliability, and toll on lane-choice behavior. Lack of clarity on how travelers? perceive travel time reliability meant different measures of reliability had to be tested to see which best represents travelers? perception. In this research, three different measures of reliability were used, namely, standard deviation of travel time, coefficient of variation of travel time and travel time standard deviation relative to the total trip time. Lane choice was estimated using multinomial logit models. Basic models, including only travel time and toll, yielded reasonable results. Models included VOTs of $1.53/hour, $6.05/hour, and $9.05/hour for off-peak, shoulder, and peak-period travelers, respectively. However, Adding different measures of reliability like standard deviation and coefficient of variation to the models resulted in counter-intuitive results. Positive coefficients for unreliability of travel time were obtained indicating that travelers, at least on the Katy Freeway, do not value travel time reliability as has been theorized in earlier studies on the same. It was concluded that additional research on how travelers perceive the reliability and time savings on MLs is needed because modeling real-world choices of MLs using empirical data and the standard definitions of reliability and time savings did not concur with the existing theory on travel time reliability and led to counter-intuitive results.Item Measuring the Value of Time in Highway Freight Transportation(2014-01-13) Miao, QingThis research investigated several aspects of the value of time (VOT) in the trucking industry. This included examining the marginal monetary benefits and costs of reduced and prolonged freight transportation time on highways. First, a comprehensive survey estimated truckers? perceived VOT by combining stated preference, utility theory, conditional logit modeling, and maximum likelihood function. From the data collected around major cities in Texas and Wisconsin, the truckers? perceived VOT was estimated to be $54.98/vehicle/hour. Second, scenario-based simulation examined urban truckload operations, the purpose of which was to examine the fleet effect of individual vehicle delay on the carrier?s operation. Two of the most congested highway segments in Houston were used for the simulation, together with constrained delivery windows. The result showed that the scenario-based vehicle VOT varied from $79.81/vehicle/hour to $120.89/vehicle/hour. Third, VOT based on commodity delay only was examined in relationship to inventory management by assuming prolonged transportation time or freight delay. Delay of chemical products was ranked as the highest VOT at $13.89/truckload/hour, followed by food products at $7.24/truckload/hour. Finally, a continuous approximation technique was developed for fleet operations in the context of less-than-truckload deliveries. The trade-offs between travel time and roadway transportation cost were derived analytically and results were used to estimate fleet value of time. Ignoring time windows, the vehicle VOT for major distribution companies in Texas was estimated to be $15.50/vehicle/hour for highway trips and $22.00/vehicle/hour for local trips. To summarize, freight VOT is not only directly due to vehicles and drivers, but depends on fleet operations and supply chain management. The several approaches adopted in this research represent possible perspectives that need to be further examined. They each reveal a component of the entire shipping process that can be appropriately utilized to calculate the overall freight VOT in future studies. For example, an urgent delivery carrying chemical products can be estimated at a total congestion cost of $162.86/vehicle/hour. However, trips with different characteristics need to be treated individually andcarefully to avoid overestimation. It remains challenging tocombineall these different elements adequately to reach valid VOT for the trucking industry.Item Quantifying Road User Costs with Heterogeneous Value of Motorists' Travel Time(2013-08-01) Tiwari, ShashankThe state transportation agencies (STAs) in the United States are mandated by federal rule to carry out work-zone impact assessment for highway rehabilitation projects. The work zone impact assessment requires calculating road user costs (RUCs) which is the sum of vehicle operating costs, accident costs, and value of time (VOT). The term ?value of time? refers to monetary equivalent of travel time wasted due to rehabilitation projects. In current practice, STAs assume VOT as homogeneous within their respective states. This leads to inaccurate RUCs calculations and poses many misapplications. Research has found that VOT is influenced by socio-demographic variables which vary within the states. But there is a lack of framework to evaluate the extent to which these factors affect value of time. The major objective of this research is to develop and validate a model that predicts value of time heterogeneously. The data were collected to cover 20 major cities in California. The state of California was chosen for this study because most highway rehabilitation projects are carried out there. The data sources included the United States Census Bureau, the California Department of Transportation (Caltrans), and the Bureau of Labor Statistics. With these data, a predictive model was developed using multiple linear regression analysis. Lastly, the model was validated using PRESS statistic. The results reveal that age, annual average daily traffic, and effective hourly income were the most significant factors influencing value of time. This study developed a model which will help Caltrans in calculating value of time heterogeneously and therefore, improve the accuracy of RUCs calculations. Moreover, this research will serve as a guideline for other STAs to develop models for respective states. Therefore, this model has a potential to greatly improve the accuracy of value of time and therefore, RUCs. The future research should focus on the identified factors, especially cost-of-living index and annual average daily traffic. Further research is required to account for heterogeneity due to other factors such as vehicle occupancy, frequency of travel, and educational qualifications.