working paper

A Real-Time Algorithm to Solve the Peer-to-Peer Ride-MatchingProblem in a Flexible Ridesharing System

Publication Date

July 1, 2015

Working Paper

UCI-ITS-WP-15-1

Areas of Expertise

Abstract

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.

Suggested Citation
Neda Masoud and R. Jayakrishnan (2015) A Real-Time Algorithm to Solve the Peer-to-Peer Ride-MatchingProblem in a Flexible Ridesharing System. Working Paper UCI-ITS-WP-15-1. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/8d2186s7.

Phd Dissertation

Freeway Traffic Parameter and State Estimation with Eulerian and Lagrangian Data

Abstract

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.

Suggested Citation
Zhe Sun (2016) Freeway Traffic Parameter and State Estimation with Eulerian and Lagrangian Data. Ph.D.. UC Irvine. Available at: https://escholarship.org/uc/item/521733s2 (Accessed: October 12, 2023).

working paper

Uncertainty And The Timing Of An Urban Congestion Relief Investment

Publication Date

March 1, 2004

Working Paper

UCI-ITS-WP-04-2

Areas of Expertise

Abstract

We analyze the impact of population uncertainty on the socially optimum timing of a congestion-relief project in a linear monocentric city with fixed boundaries, where congestion pricing cannot be implemented. This project requires time to bear fruit but no urban land. Under certainty, we show that utility maximization is roughly equivalent to a standard benefit-cost analysis (BCA). Under uncertainty, we derive an explicit optimal threshold for relieving congestion when the urban population follows a geometric Brownian motion. If the time to implement the project is short, we show analytically that deciding on the timing of congestion relief based on a BCA could lead to acting prematurely; the reverse holds if project implementation is long and uncertainty is large enough.

Suggested Citation
Jean-Daniel M. Saphores and Marlon G. Boarnet (2004) Uncertainty And The Timing Of An Urban Congestion Relief Investment. Working Paper UCI-ITS-WP-04-2. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/2x46m9pb.

working paper

Distribution and Allocation of Transit Subsidies in California

Abstract

The allocation of federal and state transit assistance on the basis of population, employment or other demographic or geographic characteristics promotes policies which may not correspond to state or federal policies toward transit. Allocation formulas must be designed to provide operators with an incentive to comply with governmental policy. In addition, existing allocation procedures fail to promote effectiveness and efficiency in transit.service. Forty-nine performance indicators are analyzed on the basis of data availability, methodological correctness, and bias, and five are selected which measure system effectiveness and efficiency and allow comparison of one system against another. These indicators may be utilized in a subsidy allocation system providing both support for basic transit services and incentives for increased efficiency.

Suggested Citation
Gordon J. Fielding and Roy E. Glauthier (1976) Distribution and Allocation of Transit Subsidies in California. Working Paper UCI-ITS-WP-76-2. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/8wx9v2qh.

published journal article

A streamlined methodology for application of TRANSYT-7F

Institute of Transportation Engineers. ITE Journal

Publication Date

February 1, 1997
Suggested Citation
John D Leonard and Wilfred W Recker (1997) “A streamlined methodology for application of TRANSYT-7F”, Institute of Transportation Engineers. ITE Journal, 67(2), p. 26. Available at: https://www.proquest.com/scholarly-journals/streamlined-methodology-application-transyt-7f/docview/224893864/se-2?accountid=14509.

published journal article

Intersectionality of individual and neighborhood-level adverse social determinants of health in early pregnancy

Pregnancy

Publication Date

January 1, 2025

Author(s)

Jameaka L. Hamilton, William A. Grobman, Jiqiang Wu, Lynn M. Yee, David Haas, Becky Mcneil, Brian Mercer, Hyagriv Simhan, Uma Reddy, Robert M. Silver, Samuel Parry, George Saade, Jun Wu, Courtney D. Lynch, Kartik K. Venkatesh

Abstract

Introduction Individual- and neighborhood-level social determinants of health (SDOH) have been assessed separately in pregnancy, but their relationship to one another remains uncertain. We investigated the intersectionality of three neighborhood-level SDOH measures with three individual-level SDOH measures. This was done to examine the concomitant experiences of multiple SDOH in pregnancy. Methods A secondary analysis of data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be. We assessed three neighborhood-level SDOH measures using geocoded participant home addresses in the first trimester at the census-tract level: (1) high socioeconomic disadvantage (in tertiles) by the 2015 Area Deprivation Index, (2) inadequate food access by the USDA Food Access Research Atlas, and (3) low walkability by the EPA National Walkability Score. We assessed three individual-level SDOH measures: low household income, lower educational attainment, and Medicaid insurance. We examined the combinations of these three neighborhood SDOH and three individual SDOH measures by graphical visualization and using statistical tests to assess overall differences in the distribution of these measures. Results Of 9588 nulliparous individuals, adverse neighborhood-level SDOH [high socioeconomic disadvantage (28%), inadequate food access (24%), and low walkability (66%)] and adverse individual-level SDOH [low household income (19%), lower educational attainment (23%), and Medicaid insurance (33%)] were common in early pregnancy. Six percent of individuals lived in a community with all three adverse neighborhood-level SDOH measures. Of those living in a community with at least two neighborhood-level SDOH measures, 23% lived in areas with inadequate food access and low walkability, 19% with high socioeconomic disadvantage and low walkability, and 1% with high socioeconomic disadvantage and inadequate food access. Overall, 23% lived in a community with no adverse neighborhood-level SDOH, and among this group, 88% had no adverse individual-level SDOH. There were significant differences in adverse individual-level SDOH based on whether individuals lived in a community with all three adverse neighborhood-level measures [low household income (39%), lower educational attainment (44%), Medicaid (55%)], any two measures [low household income (22%), lower educational attainment (27%), Medicaid (37%)], or only one measure [low household income (14%), lower educational attainment (17%), Medicaid (27%)] (p < 0.001 for all). Conclusion Among nulliparous individuals in early pregnancy, the frequency of adverse individual-level SDOH was generally higher when they lived in communities with more adverse neighborhood-level SDOH. Future approaches that identify and classify the multifaceted and multilevel nature of structural determinants as they relate to pregnancy outcomes are needed.

Suggested Citation
Jameaka L. Hamilton, William A. Grobman, Jiqiang Wu, Lynn M. Yee, David Haas, Becky Mcneil, Brian Mercer, Hyagriv Simhan, Uma Reddy, Robert M. Silver, Samuel Parry, George Saade, Jun Wu, Courtney D. Lynch and Kartik K. Venkatesh (2025) “Intersectionality of individual and neighborhood-level adverse social determinants of health in early pregnancy”, Pregnancy, 1(2), p. e70002. Available at: 10.1002/pmf2.70002.

working paper

Population and Employment Densities: Structure and Change

Publication Date

September 5, 1994

Associated Project

Working Paper

UCI-ITS-WP-93-5, UCTC 161

Areas of Expertise

Abstract

We examine spatial patterns and their changes during the 1970s for the Los Angeles region, by estimating monocentric and polycentric density functions for employment and population. Downtown Los Angeles is clearly identified as the statistical monocentric center of the region, and it is the most consistently strong center in the polycentric patterns. Polycentric models fit statistically better than monocentric models, and there was some shift in employment distribution toward a more polycentric pattern. These findings verify the existence of polycentricity in Los Angeles and demonstrate for the first time that employment and especially population follow a polycentric pattern based on exogenously defined employment centers. The results confirm that both employment and population became more dispersed during the 1970s.

Suggested Citation
Kenneth A. Small and Shunfeng Song (1994) Population and Employment Densities: Structure and Change. Working Paper UCI-ITS-WP-93-5, UCTC 161. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/6nk5v6b4.

working paper

Home Environment Consequences of Commute Travel Impedance

Publication Date

June 1, 1991

Associated Project

Author(s)

Raymond Novaco, Wendy Kliewer, Alexander Broquet

Working Paper

UCI-ITS-WP-90-6, UCTC 77

Areas of Expertise

Abstract

The physical and perceptual dimensions of commuting travel impedance were again found to have stressful consequences in a study of 99 employees of two companies. This quasi-experimental replication study, which focuses here on home environment consequences, investigated the effects of physical impedance and subjective impedance on multivariate measures of residential satisfaction and personal affect in the home. Both sets of residential outcome measures were found to be significantly related to the two impedance dimensions. As predicted, gender was a significant moderator of physical impedance effects. Females commuting on high physical impedance routes were most negatively affected. Previously found subjective impedance effects on negative home mood, regardless of gender, were strongly replicated with several methods and were buttressed by convergent results with objective indices. The theoretical conjecture that subjective impedance mediates the stress effects of physical impedance was supported for the personal affect cluster but only for one variable in the residential satisfaction cluster. Traffic congestion has increased in metropolitan areas nationwide, and commuters, families, and organizations are absorbing associated hidden costs. The results are reviewed in terms of our ecological model, and the moderating effects of gender are discussed in terms of choice and role constraints.

Suggested Citation
Raymond W. Novaco, Wendy Kliewer and Alexander Broquet (1991) Home Environment Consequences of Commute Travel Impedance. Working Paper UCI-ITS-WP-90-6, UCTC 77. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/1d5742g7.

published journal article

The multinomial, multiattribute logit choice model

Journal of Marketing Research

Publication Date

February 1, 1979

Author(s)

Dennis H. Gensch, Will Recker

Abstract

The authors argue that for the cross-sectional multiattribute approach to choice modeling, the multinomial logit is theoretically and empirically superior to the more commonly used regression approach. Other choice methodologies also are discussed briefly in relation to logit. The difference between individual level (where regression is appropriate) and cross-sectional analysis is recognized. Most marketing managers, because of their research goals, will be using a cross-sectional approach. The derivation of the logit from an underlying behavioral model of choice is illustrated. It is this underlying behavioral model of choice that provides logit with several conceptual advantages for modeling a multiattribute choice structure.

Suggested Citation
Dennis H. Gensch and Wilfred W. Recker (1979) “The multinomial, multiattribute logit choice model”, Journal of Marketing Research, 16(1), p. 124. Available at: 10.2307/3150883.