Browsing by Author "Miao, Qing"
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Item Assessing the Value of Delay to Truckers and Carriers(2011-02-22) Miao, QingThis thesis evaluates the Value of Delay (VOD) to commercial vehicle operators due to highway congestions. The VOD for congestion is a fundamental parameter driving the private sectors? response to public freight projects and policies such as corridor construction and tolling. Factors affecting the commercial VOD include direct operational cost, travel length, travel time variation, inventory holding, and warehouse management. To approach the VOD, two methods are adopted in this thesis. One is the Stated Preference (SP) survey. The other is carrier fleet operational simulation. The simulation framework uses ArcGIS, and C . ArcGIS is used to generate a freight network based on the Houston, TX highway system. A set of customers are randomly generated, each having a random demand for service, which is associated with time windows for delivery and pickup. A heuristic algorithm is proposed to dispatch vehicles for truckload service on a continuous time horizon. The average VOD is then obtained through the ratio between additional operational cost and the delay caused by the congestion. This ratio is assessed in two scenarios: single depot and two cooperating depots. Different tests based on demand size, demand distribution pattern, time window and location of congestion are conducted. Simulation shows a range of VOD from $93.99/hr to $120.89/hr for the case of a central depot and $79.81/hr to $83.81/hr for the case of two depots. In addition, a SP survey is conducted for truckers and carriers in two scenarios. The first scenario assumes a driver running late by 30 minutes on a congested road, while the second scenario assumes an on-time delivery or pickup. Several tolling alternatives are assumed to test the driver?s willingness to pay for using a hypothetical toll road. The data is then regressed with the logit model using maximum likelihood estimation to obtain perspective value of delay. A generic utility function is adopted, which results in a VOD range from $24.72/hr to $64.99/hr. A comparison between the survey and the simulation results shows that drivers perceive a significantly lower VOD than the simulated VOD in freight operation.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.