Models and Solution Algorithms for Asymmetric Traffic and Transit Assignment Problems

Modeling the transportation system is important because it provides a “common ground” for discussing policy and examining the future transportation plan required in practices. Generally, modeling is a simplified representation of the real world; however, this research added value to the modeling practice by investigating the asymmetric interactions observed in the real world in order to explore potential improvements of the transportation modeling. The Asymmetric Transportation Equilibrium Problem (ATEP) is designed to precisely model actual transportation systems by considering asymmetric interactions of flows. The enhanced representation of the transportation system by the ATEP is promising because there are various asymmetric interactions in real transportation such as intersections, highway ramps, and toll roads and in the structure of the transit fares. This dissertation characterizes the ATEP with an appropriate solution algorithm and its applications. First, the research investigates the factors affecting the convergence of the ATEP. The double projection method is applied to various asymmetric types and complexities in the different sizes of networks in order to identify the influential factors including demand intensities, network configuration, route composition between modes, and sensitivity of the cost function. Secondly, the research develops an enhancement strategy for improvement in computational speed for the double projection method. The structural characteristics of the ATEP are used to develop the convergence enhancement strategy that significantly reduces the computational burdens. For the application side, instances of asymmetric interactions observed in in-vehicle crowding and the transit fare structure are modeled to provide a suggestion on policy approach for a transit agency. The direct application of the crowding model into the real network indicates that crowd modeling with multi user classes could influence the public transportation system planning and the revenue achievement of transit agencies. Moreover, addition of the disutility factor, crowding, not always causes the increase of disutility from the transit uses. The application of the non-additive fare structure in the Utah Transit Authority (UTA) network addresses the potential of the distance-based fare structure should the UTA make a transition to this fare structure from their current fare model. The analysis finds that the zero base fare has the highest potential for increasing the transit demand. However, collecting less than $0.50 with a certain buffer distance for the first boarding has potential for attracting the users to UTA\u27s transit market upon the fare structure change

The effect of crowding on public transit user travel behavior in a large-scale public transportation system through modeling daily variations

In this paper, the crowding effect in a transit vehicle is modeled in a time-expanded network that considers the daily variation in passenger flows. The study models the daily variation of in-vehicle crowding in a real large-scale transit system. A transit assignment for this real network is modeled and implemented by constructing a crowding cost function that follows the valuation of crowding and by using the reliable shortest path finding method. The direct application of the crowding model to a real network for the Utah Transit Authority indicates that crowd modeling with multi-user classes could influence public transportation system planning and affect the revenues of transit agencies. Moreover, the addition of the disutility factor, crowding, does not always appear to cause an increase in disutility for transit users

Effective Modeling for a Distance-Based Fare Structure with a Time-Expanded Network

This study addresses the appropriateness of a passenger assignment model for a distance-based fare structure that recently has received attention from transit agencies, along with technological advances in electronic fare payment and global positioning systems. Among the two major passenger assignment models, the study identifies that the schedule-based model has an advantage over the frequency-based model for representing a distance-based fare structure. The schedule-based model that explicitly traces passenger routes enables the accurate calculation of a distance-based fare and its variant. In addition, the study addressed the implementation issues associated with the schedule-based model. As the schedule-based model is considered to require more data than the widely-used frequency-based model, the study suggests a way to mitigate this data requirement issue by approximating the timetable at each stop with the same data used for the implementation of the frequency-based model. A case study on the field application of the schedule-based model and its availability as a ready-to-use option in most commercial software for travel demand modeling is described

Determining Appropriate Fare Levels for Distance-Based Fare Structure Considering Users\u27 Behaviors in a Time-Expanded Network

This research investigated the potential of a distance-based fare structure with a case study of the Utah Transit Authority system in northern Utah. The metrics of evaluation were viewed through demand maximization within a modeling scheme for a distance-based fare structure for all fixed route transit modes. Transit users\u27 route choices were explicitly modeled in the transit system on the time-expanded network. This modeling scheme was integrated into the lower level of the bi-level programming framework, where the upper level uncovered the optimized fare levels for the distance-based fare structure with a genetic algorithm. Through implementation of the methodology, the distance-based fare levels were evaluated for their effect on increasing transit demand. Using the market segmentation analysis, the study found that a distance-based fare with a no-base fare had the highest potential for increasing the transit demand. A $0.50 base fare was examined and was shown to be feasible in the case that a base fare was not necessary because of agency policy

Financing for a Sustainable PPP Development: Valuation of the Contractual Rights under Exercise Conditions for an Urban Railway PPP Project in Korea

The Minimum Revenue Guarantee (MRG) was designed to mitigate the financial risk of private investors that participate in the transportation project as concessionaire under a public-private partnership (PPP) program. The MRG can pose a significant financial burden to governments especially when the contract revenue is set considerably higher than the actual revenue. This may encourage the concessionaire to inflate the traffic forecast to make the project look as if it will be profitable. In order to mitigate this problem, extra conditions for exercising the MRG can be considered. This study examines how these exercise conditions change the economic value of the MRG using the case study based on the urban railway project in the Republic of Korea. By utilizing the real options analysis, the study identified that the exercise conditions have worked to curtail the expected payment from the government, eventually leading to a reduction in the concessionaire’s expectation of revenue. The value of MRG was at a far lower level compared to the concessionaire’s investment because of the low probability of exercising the MRG when the exercise conditions apply. The findings are expected to contribute to the sustainability of the PPP program by recognizing and quantifying liabilities and risks embedded in the concession agreement in advance

Analysis of Features Affecting Contracted Rate of Return of Korean PPP Projects

Various risk factors influence the success of public–private partnership (PPP) projects. This study analyzes the risk attributes of PPP projects and develops a regression model based on a 20-year PPP project database to quantitatively analyze the factors affecting the contracted internal rate of return (CIRR) of PPP projects. Although the risk factors of PPP projects have been widely studied, the factors affecting CIRR have not been explored. Information from the intra-info DB system managed by Korea Development Institute was used to calculate the impact of the variables on CIRR. It was observed that the CIRR of Korea’s PPP projects did not reflect the risks associated with the facility types, service area, amount of private investment, and operation period accurately. Financing costs did not demonstrate a statistically significant relationship with the CIRR either. Furthermore, the CIRR of projects with a minimum revenue guarantee option was found to be higher than that of projects without. The CIRR of the current project was found to be closely related to the number of bidding competitors and the CIRR values of previous projects that are similar to the current one. This is attributed to a failure in the bureaucratic negotiation behavior of the parties due to their avoidance of responsibilities