working paper

Estimating the Potential Cost Savings of Transit Service Contracting

Abstract

The continued financial problems of the public transportation industry have motivated a search for more cost-effective ways of delivering transit services. Service contracting–the contracting of public transit services to private providers–has emerged as one of the most promising alternatives. Existing evidence suggests that service contracting could reduce public agency cost by 10 to 50 percent. If service contracting were implemented throughout the public transit industry, services currently provided by public agencies would be shifted to private provision. However, little is known about how such service shifts would affect transit service costs, and whether significant cost savings would occur. This paper presents an assessment of the cost savings potential of transit agency service contracting. A cost model based on the concept of avoidable cost is used in a series of case studies to generate estimates of potential cost savings resulting from contracting various quantities of transit service. Research results showed average cost savings of 23 percent for the contracted service. These savings are equivalent to about 4 percent of the transit agency’s total operating cost. Cost savings depend on a number of factors, but are roughly associated with the size of the transit agency. Cost savings for small agencies are insignificant and can be negative, while savings for agencies larger than 250 vehicles typically range between 5 and 7 percent of total operating cost when 20 percent of existing service is contracted.

Suggested Citation
Genevieve Giuliano and Roger F. Teal (1986) Estimating the Potential Cost Savings of Transit Service Contracting. Working Paper UCI- ITS-WP-86-9. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/70k9f185.

published journal article

Generalized bathtub model of network trip flows

Transportation Research Part B: Methodological

Publication Date

June 1, 2020

Author(s)

Abstract

Vickrey (1991, 2020) proposed a bathtub model for the evolution of trip flows served by privately operated vehicles inside a road network based on three premises: (i) treatment of the road network as a single bathtub; (ii) the speed-density relation at the network level, also known as the network fundamental diagram of vehicular traffic, and (iii) the time-independent negative exponential distribution of trip distances. However, the distributions of trip distances are generally time-dependent in the real world, and Vickrey’s model leads to unreasonable results for other types of trip distance distributions. Thus there is a need to develop a bathtub model with more general trip distance distribution patterns. In this study, we present a unified framework for modeling network trip flows with general distributions of trip distances, including negative exponential, constant, and regularly sorting trip distances studied in the literature. In addition to tracking the number of active trips as in Vickrey’s model, this model also tracks the evolution of the distribution of active trips’ remaining distances. We derive four equivalent differential formulations from the network fundamental diagram and the conservation law of trips for the number of active trips with remaining distances not smaller than any value. Then we define and discuss the properties of stationary and gridlock states, derive the integral form of the bathtub model with the characteristic method, and present two numerical methods to solve the bathtub model based on the differential and integral forms respectively. We further study equivalent formulations and solutions for two special types of distributions of trip distances: time-independent negative exponential or deterministic. In particular, we present six equivalent conditions for Vickrey’s bathtub model to be applicable.

Suggested Citation
Wen-Long Jin (2020) “Generalized bathtub model of network trip flows”, Transportation Research Part B: Methodological, 136, pp. 138–157. Available at: 10.1016/j.trb.2020.04.002.

working paper

Optimal Sensor Requirements

Abstract

PATH Task ORder 6328 addresses the optimal deployment of traffic detectors on freeway to ensure that adequate information is collected at the lowest possible cost. The project team produced a study framework and tools that can be applied locally to test the sensitivity of traffic data quality to detectors location and spacing, and ultimately recommend a deployment plan.

Various types of traffic detectors, including loop detectors, radars, toll tag readers and video cameras are deployed on highways. They provide the data needed to run traffic management applications such as ramp metering control, bottleneck identification, and travel times estimation. However, few studies have systematically analyzed the data requirements of these applications in terms of detector spacing and location. In other words, the trade-offs between the cost of the detectors and their benefits for traffic estimation accuracy are not well known. As a result, most highway detectors are installed using ad hoc guidelines or on a case-by-base basis, rather than through the application of measurable objectives. This in turn makes it difficult for practitioners to justify equipment and maintenance expenditures, often slowing deployment.

The product of this research is two-fold. First, we developed a framework to study the sensitivity of traffic information to sensor location and spacing and reached general conclusions. Second, the team created practical tools to assist practitioners at the local level with optimal sensor deployment. These tools include recommendations for rural areas and an Excel-based model for urban areas.

policy brief

Advanced Low-NOx Compressed Natural Gas Engines in Medium- and Heavy-Duty Vehicles Are Poised to Deliver Air Quality Benefits and Advance California’s Climate Goals

Abstract

Recent commercialization of advanced low-nitrogen oxides (NOx) Compressed Natural Gas (CNG) engines for medium- (MDV) and heavy-duty (HDV) vehicles has garnered significant interest due to the potential air quality benefits. Further, utilizing renewable natural gas (RNG) in advanced CNG engines from sources such as biomass and/ or biogas can achieve reductions in greenhouse gas (GHG) relative to using petroleum fuels and fossil CNG. However, the regional air quality and GHG reduction benefits of large‐scale deployment of advanced CNG trucks are currently unclear. Further, more information is required regarding RNG production potential from California instate biofuel resources, including potential supply volumes and production pathways that provide maximum GHG reductions. The UC Irvine Advanced Power and Energy Program assessed the air quality and GHG implications of transitioning to advanced CNG engines in MDVs and HDVs in California by developing and comparing different future adoption scenarios. The research team also leveraged prior research of biogas and biomass resources in California to consider different options for producing RNG in-state. Key findings from this research are highlighted in the following section.

Suggested Citation
Alejandra Cervantes, Brendan Shaffer, Michael MacKinnon and Scott Samuelsen (2017) Advanced Low-NOx Compressed Natural Gas Engines in Medium- and Heavy-Duty Vehicles Are Poised to Deliver Air Quality Benefits and Advance California’s Climate Goals. Policy Brief. UC ITS. Available at: https://doi.org/10.7922/g2gm85ng.

conference paper

Selective vehicle routing problems under uncertainty without recourse

Proceedings of the INFORMS annual meeting, phoenix, AZ

Publication Date

October 1, 2012
Suggested Citation
M Allahviranloo, J Chow and W.W. Recker (2012) “Selective vehicle routing problems under uncertainty without recourse”, in Proceedings of the INFORMS annual meeting, phoenix, AZ.

conference paper

A framework for navigation with LTE time-correlated pseudorange errors in multipath environments

2019 IEEE 89th vehicular technology conference (VTC2019-Spring)

Publication Date

April 1, 2019

Author(s)

Kimia Shamaei, Joshua J. Morales, Zaher Kassas

Abstract

A navigation framework based on a multi-state constraint Kalman filter (MSCKF) is proposed to reduce the effect of time-correlated pseudorange measurement noise of cellular long-term evolution (LTE) signals. The proposed MSCKF framework captures the position of the antenna over a window of measurements to impose constraints on the position estimate. Simulation results are presented showing a reduction of 57% and 51% in the two-dimensional (2D) and three-dimensional (3D) position root mean squared-error (RMSE), respectively, using the proposed framework compared to an extended Kalman filter (EKF). Experimental results on a ground vehicle navigating in an urban environment are presented showing a reduction of 29% and 64.7% in the 2D and 3D position RMSE, respectively, and a reduction of 19.6% and 86.7% in the 2D and 3D maximum error, respectively, using the proposed framework compared to an EKF.

Suggested Citation
Kimia Shamaei, Joshua J. Morales and Zaher M. Kassas (2019) “A framework for navigation with LTE time-correlated pseudorange errors in multipath environments”, in 2019 IEEE 89th vehicular technology conference (VTC2019-Spring). IEEE (IEEE vehicular technology conference proceedings). Available at: 10.1109/vtcspring.2019.8746561.

working paper

Walking and Automobile Traffic Near Schools: Data to Support an Evaluation of School Pedestrian Safety Programs

Publication Date

September 1, 2002

Working Paper

UCI-ITS-WP-02-7

Areas of Expertise

Abstract

Pedestrian accidents among children are an important transportation issue. Several recent policy initiatives have focused on reducing childhood pedestrian accident in the United States, yet those efforts exist within a context of limited and often insufficient data. This paper describes new data that can give much more detailed information on the determinants of pedestrian safety near schools. The data were developed to support an ongoing evaluation of a major childhood pedestrian safety program – the California Safe Routes to School construction program.

Suggested Citation
Craig Anderson, Marlon G. Boarnet, Tracy McMillan, Mariela Alfonzo and Kristen Day (2002) Walking and Automobile Traffic Near Schools: Data to Support an Evaluation of School Pedestrian Safety Programs. Working Paper UCI-ITS-WP-02-7. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/69h09913.

conference paper

Re-Envisioning the Park-and-Ride Concept for the Automated Vehicle (AV) Era with Private-to-Shared AV Transfer Stations

Transportation Research Board 103rd Annual Meeting

Publication Date

January 1, 2024
Suggested Citation
Youngyun Bahk and Michael Hyland (2024) “Re-Envisioning the Park-and-Ride Concept for the Automated Vehicle (AV) Era with Private-to-Shared AV Transfer Stations”.

Phd Dissertation

Local urban development stakeholders in a globalizing context: Civil society, urban governance and urban poverty in Harare, Zimbabwe

Publication Date

June 30, 2003

Author(s)

Abstract

This study examines the impacts of globalization on domestic policy and the concomitant effects on local development processes in Harare, Zimbabwe. It assesses the various processes and strategies of engaging disparate development stakeholders in urban governance and evaluates the experiences and capacities of civil society in urban development. Macroeconomic instability and other external forces such as globalization constraints, the legacy of colonialism, and post independent structural adjustment programs, on one hand; rapid urban population growth, along with institutional, financial, and administrative incapacities and outdated legal and governance traditions at the urban and national levels, on the other, have resulted in failure of government to provide social services or even to maintain basic infrastructure. Consequently, civil society is increasingly being viewed as a mechanism for satisfying the needs of the urban poor, and is even viewed by some as a universal remedy for development challenges in developing countries like Zimbabwe. This study, therefore, critically examines these organizations within the Zimbabwean context to assess their effectiveness. The main finding of this study is that, in Zimbabwe, the only civil society activities permitted are those that do not threaten to challenge the status quo. While the efficacy of organizations and groups that advocate for change is questionable in the face of a powerful, and in some cases hostile, state that restricts and sometimes prevents them from working, the role of welfare and developmental NGOs remains paramount. Civil society does not exist in a vacuum; it is dependent on the political context comprising the state, political institutions, and political culture that surround it. Contrary to the belief that globalization renders the state obsolete, the Zimbabwean government still plays a central role in development issues. The effectiveness of civil society depends on the nature of its internal organization and operations, as well as its relationships with the state and other urban development stakeholders. This study concludes that since their roles are complementary and mutually reinforcing, civil society and the state need each other, and they must work together in order to achieve human sustainable development of all sectors of society.

Suggested Citation
Doug Feremenga (2003) Local urban development stakeholders in a globalizing context: Civil society, urban governance and urban poverty in Harare, Zimbabwe. PhD Dissertation. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/17uq3m8/alma991035093303904701.

Working Paper: Airport choice and airline choice in the market for air travel between the San Francisco Bay area and greater Los Angeles in 1995

Abstract

This paper empirically investigates the impact of airport and airline supply characteristics on the air travel choices of passengers departing from one of three San Francisco Bay area airports and arriving at one of four airports in greater Los Angeles. It does so by estimating a conditional logit model for the market of air travel between both metropolitan areas in 1995, and using the estimated model to simulate three counterfactual scenarios. First, reducing access times to San Francisco International airport by 10% for all travelers increases the market share of that airport by 4.5%-point. United Airlines benefits from the reduced access times, as its market share increases by 2.9%-point. Second, reducing average delays at San Francisco International airport by 10% has similar aggregate effects to the first scenario, but indicates that leisure travelers value access time reductions more than reduced delays. Third, entry of Southwest airlines in San Francisco International airport increases the market share of Southwest airlines by 5%-point to 15-%point, depending on assumptions concerning its continuation of services at Oakland International Airport, and assuming that rival carriers do not respond in terms of prices or service levels.