published journal article

The value of transportation accessibility in a least developed country city – The case of Rajshahi City, Bangladesh

Transportation Research Part A: Policy and Practice

Publication Date

July 1, 2016

Abstract

Little appears to be known about the capitalization of transportation accessibility in South Asian housing markets, which typically differ from those of industrialized countries. This study starts addressing this gap by providing empirical evidence about the nature and the magnitude of the value of accessibility as reflected by residential rents in Rajshahi City, Bangladesh. Results of the authors’ spatial auto-regressive disturbance (SARAR) spatial hedonic model estimated on 526 observations from a random sample collected via in-person interviews indicate that the rent of a multi-unit dwelling decreases by 0.0239% for every 1% increase in network access distance to the nearest major road. Moreover, proximity (within 400 m) to a primary school and to a healthcare facility commands rent premiums of respectively 93.55 BDT ($1.40) and 109.45 BDT ($1.64). Surprisingly, whether access roads are paved or not does not statistically impact rents, probably because of the dominance of walking, rickshaws use, and biking, combined with the rarity of personal cars. Likewise, proximity to bus stops and to train stations is not reflected in rents of multi-family dwellings, likely because buses and trains in Rajshahi City only provide regional and national service. Differences in estimates of the authors’ spatial models between maximum likelihood (ML) and generalized spatial two-stage-least-squares illustrate the danger of relying on ML in the presence of heteroskedasticity. These results should be useful for planning transportation infrastructure funding measures in least developed country cities like Rajshahi City.

Suggested Citation
Suman K. Mitra and Jean-Daniel M. Saphores (2016) “The value of transportation accessibility in a least developed country city – The case of Rajshahi City, Bangladesh”, Transportation Research Part A: Policy and Practice, 89, pp. 184–200. Available at: 10.1016/j.tra.2016.05.002.

published journal article

Continuous formulations and analytical properties of the link transmission model

Transportation Research Part B: Methodological

Publication Date

April 1, 2015

Author(s)

Suggested Citation
Wen-Long Jin (2015) “Continuous formulations and analytical properties of the link transmission model”, Transportation Research Part B: Methodological, 74, pp. 88–103. Available at: 10.1016/j.trb.2014.12.006.

working paper

Structural Equation Modeling for Travel Behavior Research

Publication Date

November 11, 2001

Author(s)

Working Paper

UCI-ITS-WP-01-7

Areas of Expertise

Abstract

Structural equation modeling (SEM) is an extremely flexible linear-in-parameters multivariate statistical modeling technique. It has been used in modeling travel behavior and values since about 1980, and its use is rapidly accelerating, partially due to the availability of improved software. The number of published studies, now known to be more than fifty, has approximately doubled in the past three years. This review of SEM is intended to provide an introduction to the field for those who have not used the method, and a compendium of applications for those who wish to compare experiences and avoid the pitfall of reinventing previous research.

Suggested Citation
Thomas F. Golob (2001) Structural Equation Modeling for Travel Behavior Research. Working Paper UCI-ITS-WP-01-7. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/8392r1qv.

conference paper

Evaluation and modification of constant volume sampler based procedure for plug-in hybrid electric vehicle testing

Proceedings of the SAE international powertrains, fuels and lubricants meeting, lKyoto, japan

Publication Date

January 1, 2012

Abstract

Plug-in hybrid electric vehicles (PHVs) consume both fossil fuel and grid electricity, which imposes emission testing challenges on the current constant volume sampler (CVS) test method. One reason is that in the charge-depleting cycle, PHVs having all-electric range operate the engine for a small portion of the traction energy need, causing the CVS to overdilute the exhaust gas. The other reason is that the dilution factor (DF) in the EPA calculation has an error caused by ignoring the COâ?? concentration in ambient air. This paper evaluates these challenges by testing a Toyota PHV on the industry standard CVS system combined with additional continuous sampling methodology for continuous diluents, smooth approach orifice (SAO) measurement for ambient air flow, and fuel flow meter (FFM) measurement for fuel consumption. The current EPA DF can produce an error resulting in higher mass calculation. For the test car, the error for THC is in the range 0-20% on the urban dynamometer driving schedule (UDDS), and 0-75% on the highway fuel economy test (HWFET), though it is estimated that this error amounts to less than 4.7% error for non-methane organic gas (NMOG) compared to the current SULEV emission standard. For the test car, the error for CO, NOx, and COâ?? is in the range of 0-8%, 0-3.6%, and 0-0.5%, respectively, which are negligible compared to the current SULEV emission standard. An alternative procedure is proposed for the charge depleting cycle using the continuous sampling method to ignore the time period before the engine first starts, thereby eliminating overdilution. This technique can reduce the impact of potential gas analyzer and DF error to one third compared to the current CVS method. The FFM and CVS showed matching measurements during most portions of testing and only demonstrated discrepancy of fuel consumption measurement during the first engine start cycle. The detailed reason why the FFM measured 13 grams more COâ?? than the CVS on average is likely associated with exhaust left in the vehicle tailpipe and CVS sampling line, though more investigation is needed with future testing.

Suggested Citation
Li Zhang, Tim Brown and G. Scott Samuelsen (2012) “Evaluation and modification of constant volume sampler based procedure for plug-in hybrid electric vehicle testing”, in Proceedings of the SAE international powertrains, fuels and lubricants meeting, lKyoto, japan. SAE International, pp. pp 542–559.

working paper

Economies of Scale and Self-Financing Rules with Noncompetitive Factor Markets

Publication Date

November 1, 1996

Author(s)

Working Paper

UCI-ITS-WP-96-10

Abstract

When a firm or public authority prices output at marginal cost, its profits are related to the degree of local economies of scale in its cost function. As is well known, this result extends to the case where some congestion-prone inputs are supplied by users. I show that contrary to common belief, the result holds even when scale economies are affected by a rising factor supply curve. In that case, constant returns to scale in production produces diseconomies of scale in the cost function, making marginal-cost pricing profitable. Examples are provided for a monopsonist both with and without price discrimination. In the latter case, second-best pricing is also considered: profits then are not governed in the usual way either by returns to scale in production or by scale economies in the cost function, but some useful bounds are provided.

Suggested Citation
Kenneth A. Small (1996) Economies of Scale and Self-Financing Rules with Noncompetitive Factor Markets. Working Paper UCI-ITS-WP-96-10. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/9qp0s911.

Preprint Journal Article

Metrics for Quantifying Shareability in Transportation Networks: The Maximum Network Flow Overlap Problem

Publication Date

July 1, 2022

Abstract

Cities around the world vary in terms of their urban forms, transportation networks, and travel demand patterns; these variations affect opportunities for travelers to share trips, and the viability of shared mobility services. This study proposes metrics to quantify the maximum shareability of person-trips in a city, or region of a city, as a function of two inputs—the transportation network structure and origin-destination (OD) travel demand. The study first conceptualizes a fundamental shareability unit, ‘flow overlap’. Flow overlap denotes, for a person-trip traversing a given path, the weighted (by link distance) average number of other person-trips sharing the links along the original person-trip’s path. The study extends this concept to the network level and formulates the Maximum Network Flow Overlap Problem (MNFLOP) to assign all OD person-trips to network paths that maximize flow overlap in the whole network. The study also proposes an MNFLOP variant with a second objective function term, detour distance, to capture the trade-off between minimizing travel distance and maximizing shareability. The study utilizes the MNFLOP output to calculate metrics of shareability at various levels of aggregation: person-trip level, OD level, origin or destination level, network level, and link level. The study applies the MNFLOP and associated shareability metrics to different OD demand scenarios in the Sioux Falls network. The computational results verify that (i) MNFLOP assigns person-trips to paths such that flow overlaps significantly increase relative to shortest path assignment, (ii) MNFLOP and its associated shareability metrics can meaningfully differentiate between different OD trip matrices in terms of maximum shareability, and (iii) an MNFLOP-based metric can quantify demand dispersion—a metric of the directionality of demand—in addition to the magnitude of demand, for trips originating or terminating from a single node/location in the network. The paper also includes an extensive discussion of potential future uses of the MNFLOP and its associated shareability metrics.

Suggested Citation
Navjyoth Sarma and Michael Hyland (2022) “Metrics for Quantifying Shareability in Transportation Networks: The Maximum Network Flow Overlap Problem”. Rochester, NY: SSRN. Available at: 10.2139/ssrn.4145450.

policy brief

Public Transportation, Transportation Network Companies (TNCs), and Active Modes

Suggested Citation
Jean-Daniel Saphores (2022) Public Transportation, Transportation Network Companies (TNCs), and Active Modes. Policy Brief. ITS-Irvine. Available at: https://metrans.org/assets/research/psr-19-34_saphores_research-brief.pdf.

published journal article

Stochastic dynamic itinerary interception refueling location problem with queue delay for electric taxi charging stations

Transportation Research Part C: Emerging Technologies

Suggested Citation
Jaeyoung Jung, Joseph Y.J. Chow, R. Jayakrishnan and Ji Young Park (2014) “Stochastic dynamic itinerary interception refueling location problem with queue delay for electric taxi charging stations”, Transportation Research Part C: Emerging Technologies, 40, pp. 123–142. Available at: 10.1016/j.trc.2014.01.008.

research report

Simulation evaluation of green driving strategies based on inter-vehicle communications

Publication Date

August 1, 2010

Abstract

This paper examines two green driving strategies based on inter-vehicle communication (IVC) aimed at reducing tailpipe emissions. Excessive speed and stop-and-go traffic significantly increase fuel consumption and vehicle emissions. It is anticipated that IVC, including vehicle-to-vehicle and vehicle-to-infrastructure communications, will be available in the future to relay time-critical and location-based traffic information between vehicles allowing people to drive more smoothly and safely, which also affects fuel use. In this paper the authors study green driving strategies based on IVC and their effects on emission reductions in different traffic conditions. Newellâ??s car-following model and VT-Micro are integrated to establish a simulation platform. With higher market penetration of IVC-equipped vehicles, reduction of emissions and fuel consumption are greater. The greater the delay in communication, the smaller the reduction in emissions and fuel consumption.

Suggested Citation
Hao Yang, Daji Yuan, Wen-Long Jin and Jean-Daniel Saphores (2010) Simulation evaluation of green driving strategies based on inter-vehicle communications. University of California Transportation Center, p. 23p.

published journal article

Airline fuel usage and carbon emissions: Determining factors

Journal of Air Transport Management

Publication Date

July 1, 2017

Author(s)

Jan Brueckner, Chrystyane Abreu
Suggested Citation
Jan K. Brueckner and Chrystyane Abreu (2017) “Airline fuel usage and carbon emissions: Determining factors”, Journal of Air Transport Management, 62, pp. 10–17. Available at: 10.1016/j.jairtraman.2017.01.004.