conference paper
Phd Dissertation
The purpose of this study is to develop a traffic estimation framework which combines different data sources to better reconstruct the traffic states on the freeways. The framework combines both traffic parameter and state estimation in the same work flow, which resolves the inconsistency issue of most existing traffic state estimation methods. To examine the quality of the traffic sensor data, the study starts with proposing the network sensor health problem (NSHP). The optimal set of sensors is selected from all sensors such that the violation of flow conservation is minimized. The health index for individual detector is then calculated based on the solutions. We also developed a tailored greedy search algorithm to find the solutions effectively. The proposed method is tested using the loop detector data from PeMS on a stretch of the SR-91 freeway. We compared the results with PeMS health status and found considerable level of consistency. Two different traffic state estimation methods are proposed based on the data availability and traffic states. The LoopReid method is derived from the Newell’s simplified kinematic wave model by assuming the whole road segment is fully congested. We formulate a least square optimization problem to find the initial states and traffic parameters based on the first-in-first-out principle and the congested part of the Newell’s model. While developing the LoopCT method, we derived a counterpart of the Newell’s kinematic wave model in the Lagrangian coordinates under Eulerian boundary conditions. This model also leads to a new method to estimate vehicle trajectories within a road segment. We formulate a least square optimization problem in initial states and traffic parameters which works for mixed traffic states. The two estimation methods turned out to be highly related and the LoopCT method degenerates to the LoopReid method when the traffic is fully congested. The two methods are validated using two datasets from the NGSIM project. Both methods achieved considerable level of accuracy at reconstructing the traffic states and parameters.
working paper
Real-time peer-to-peer ridesharing is a promising mode of transportation that has gained popularity during the recent years, thanks to the wide-spread use of smart phones, mobile application development platforms, and online payment systems. An assignment of drivers to riders, known as the ride-matching problem, is the central component of a peer-to-peer ridesharing system. In this paper, we discuss the features of a flexible ridesharing system, and propose an algorithm to optimally solve the ride-matching problem in a flexible ridesharing system in real-time. We generate random instances of the problem, and perform sensitivity analysis over some of the important parameters in a ridesharing system. Finally, we introduce the concept of peer-to-peer ride exchange, and show how it affects the performance of a ridesharing system.
Preprint Journal Article
This is a copy of the accepted final research report for the California Air Resources Board that details findings and analysis from an ongoing study, the Comprehensive Assessment of Land Use Entitlements Study (CALES). CALES examines how jurisdictions approve dense housing development and details entitlement processes (often the first step to development). CALES analyzes how enforceable climate policies operate in relationship to the approval of new housing in urban cities and exurban areas, and whether new housing development in both contexts faces opposition through lawsuits. All data points to local authority over land and local regulation as the most significant barrier to increasing infill dense housing and affordable housing. Local governments could eliminate obstacles associated with state level environmental regulation (and related litigation) by reforming their own local law. Though community opposition to housing through litigation varies across cities, less than 3% of all approvals in our data faced opposition through litigation—with no noticeable difference between litigation rates for housing in infill or exurban contexts. Both dense infill and exurban subdivision development used similar expedited environmental review pathways intended to promote infill development. This includes exurban development sited in high fire hazard areas.
presentation
working paper
This paper describes a statistical framework that can be used for analysis of statewide traffic count data. It also provides a basis for designing a streamlined and cost-effective statewide traffic data collection program. The procedures described were developed as part of an in-depth evaluation study for the Washington State Department of Transportation. They were used to develop recommendations for an improved, statistically-based, statewide highway data collection program. The program is intended to be implemented readily, and is consistent with the FHWA Highway Performance Monitoring System and the recent FHWA draft Traffic Monitoring Guide. In the latter case, several modifications (improvements) to the statistical framework for volume counting and vehicle classification were investigated, particularly for deriving estimates of annual average daily traffic (AADT) from short duration axle counts at any location on the state highway system. AADT estimates can be derived for each vehicle type, if desired. The estimation of associated seasonal, axle correction and growth factors is also described. The methodology enables the statistical precision of all estimates to be determined. The results obtained from applying these procedures to Washington State traffic data are presented.
working paper
Discretionary grant programs have been popular with State legislatures as a mechanism for extending the benefits of transit programs to small cities and rural areas as well as stimulating innovations in urban areas. This article analyzes state discretionary grant transit programs in California and Minnesota using the criterion of effective administration. The purpose is to develop a framework for understanding administrative problems that result when state discretionary transit programs do not have adequate objectives. Without explicit objectives, selection, monitoring, evaluation, and overall management is weak. Project performance is reduced and scarce public funds are wasted. Recommendations include: that legislatures make explicit the mission and goals or discretionary programs; that administrative agencies define measurable objectives and administrative guidelines; and that local grant recipients be granted funds only after specific objectives and performance standards have been presented.
published journal article
Rent extraction by public sector workers may be limited by the ability of taxpayers to vote with their feet. But rent extraction may be higher in regions where high amenities mute the migration response. This paper develops a theoretical model that predicts such a link between public sector wage differentials and local amenities, and the predictions are tested by analyzing variation in these differentials and amenities across states. Public sector wage differentials are, in fact, larger in the presence of high amenities, with the effect stronger for unionized public sector workers, whose political power may allow greater scope for rent extraction.
conference paper
conference paper