working paper

Efficient Estimation of Nested Logit Models

Publication Date

June 1, 1985

Working Paper

UCI-ITS-WP-85-4

Areas of Expertise

Abstract

This paper examines the Sequential, Full Information Maximum Likelihood (FIML), and Linearized Maximum Likelihood (LML) estimators for a Nested Logit model of time-of-day choice for work trips. These estimators are compared using a Monte Carlo study based on specification and data from a previously published empirical study. The sequential estimator is found to be much less efficient than either LML or FIML; and its uncorrected second-stage standard-error estimates are strongly downward biased. LML is only slightly less efficient than FIML, but is often easier to compute. However there are cases where the sequential and LML estimators do not exist.

Suggested Citation
David Brownstone and Kenneth A. Small (1985) Efficient Estimation of Nested Logit Models. Working Paper UCI-ITS-WP-85-4. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/7017v80x.

working paper

Micro-simulation Modeling Approach to Applications of On-line Simulation and Data Fusion

Abstract

This report summarizes research work conducted under TO4143 at the California PATH ATMS Center at the University of California, Irvine. This project has two tasks: Functionality enhancements of the PARAMICS simulation model through API programming for the on-line simulation application; On-line data fusion algorithm for a better section travel time estimation based on point detector data and probe vehicle data. In order to conduct these two tasks, we complete the following two related studies, which are the basis of the two tasks of this project: Development of the capability-enhanced PARAMICS simulation environment through API programming; Calibration and validation of microscopic simulation models.

research report

Large-Scale Traffic Simulation Through Distributed Computing of Paramics

Publication Date

October 1, 2004

Author(s)

Final Report

UCB-ITS-PRR-2004-42

Abstract

Simulation modeling is an increasingly popular and effective tool for analyzing transportation problems, which are not amendable to study by other means. We examine the need for parallel or distributed simulation approaches from the need for computational speed-ups, availability of options towards that, and then at the need to distribute the effort to develop network simulation contexts and datasets. After an overview of the general techniques for the distributed discrete-event simulation and previous efforts on the distributed traffic simulation, we present the general architecture of the proposed distributed modeling framework. Two categories of modeling strategies, namely, light global control / independent subnets vs. heavy global control / coordinated subnets are described. We have implemented the distributed scheme of light global control / independent subnets and the implemented details, such as communication techniques and vehicle transferring across the boundary of two subnets are discussed. Unlike the previous studies using the dedicated high performance machines, our efforts are to utilize the low-cost networked PCs that are commonly available. By using the API supported by off-the-shelf Paramics software, we are able to distribute the computational load of microscopic simulation to multiple single-processor PCs without access the proprietary source codes of the simulation program. Performance testing and analysis of the implemented prototype demonstrate that the proposed framework is very promising.

Suggested Citation
Henry X. Liu, Wenteng Ma, R. Jayakrishnan and Will Recker (2004) Large-Scale Traffic Simulation Through Distributed Computing of Paramics. Final Report UCB-ITS-PRR-2004-42. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/4h1451bn.

conference paper

Using mesoscopic traffic simulation in a seismic risk analysis framework applied to a downtown Los Angeles network

Proceedings of the 89th annual meeting of the transportation research board

Publication Date

January 1, 2010

Abstract

Previous efforts to quantify and estimate the effect of seismic disruptions on the performance of the transportation network have relied on traditional trip-based static traffic assignment methods to estimate and compare network flows under base and damaged cases. Such static assignments with the well-known problem of unrealistically high volume/capacity ratios on congested links, are questionable for predicting the post-earthquake peak-period travel times when links are disabled. This paper introduces the use of mesoscopic traffic simulation in a seismic risk analysis (SRA) framework. This study assesses seismic risk in terms of potential travel time increases in a study area incorporating the site of the Downtown Los Angeles bridge failures during the 1994 Northridge earthquake. This study successfully obtained system risk curves of network-wide travel time increases, and also took advantage of vehicle trajectory output to obtain risk curves of travel time increases for specific origin-destination (OD) pairs.

Suggested Citation
Pierre Auza, R. Jayakrishnan and Masanobu Shinozuka (2010) “Using mesoscopic traffic simulation in a seismic risk analysis framework applied to a downtown Los Angeles network”, in Proceedings of the 89th annual meeting of the transportation research board, p. 20p.

Research Report: Resource Paper an Attitudinal Models

published journal article

Safe streets for some: A review of local active transportation responses across the U.S. during the COVID-19 pandemic

Journal of Transport & Health

Publication Date

May 1, 2023

Author(s)

Matthew Dean, Kaelin A. Amaya, Jennifer Hall, Kalinda Marie Gupta, Rachael T. Panik, Jeanette Gustat, Angie L. Cradock

Abstract

Introduction & research objectives The COVID-19 pandemic significantly disrupted daily travel. This paper contrasts 51 US cities’ responses, namely street reallocation criteria and messaging related to physical activity (PA) and active transportation (AT) during the early months of the pandemic. This study can be utilized by cities for aiding in the creation of locally responsive policies that acknowledge and remedy a lack of safe active transportation. Methods A content analysis review was conducted of city orders and documents related to PA or AT for the largest city by population in all 50 US states and the District of Columbia. Authoritative documents issued from each city’s public health declaration (ca. March 2020) to September 2020 were reviewed. The study obtained documents from two crowdsourced datasets and municipal websites. Descriptive statistics were used to compare policies and strategies, with a focus on reallocation of street space. Results A total of 631 documents were coded. Considerable variation existed in city responses to COVID-19 that impacted PA and AT. Most cities’ stay-at-home orders explicitly permitted outdoor PA (63%) and many encouraged PA (47%). As the pandemic continued, 23 cities (45%) had pilot programs that reallocated street space for non-motorized road users to recreate and travel. Most cities explicitly mentioned a rationale for the programs (e.g., to provide space for exercise (96%) and to alleviate crowding or provide safe AT routes (57%)). Cities used public feedback to guide placement decisions (35%) and several welcomed public input to adjust initial actions. Geographic equity was a criterion in 35% of programs and 57% considered inadequately sized infrastructure in decision-making. Conclusions If cities want to emphasize AT and the health of their citizens, safe access to dedicated infrastructure needs to be prioritized. More than half of study cities did not instate new programs within the first 6 months of the pandemic. Cities should study peer responses and innovations to inform and create locally responsive policies that can acknowledge and remedy a lack of safe AT.

Suggested Citation
Matthew D. Dean, Kaelin A. Amaya, Jennifer Hall, Kalinda Marie Gupta, Rachael T. Panik, Jeanette Gustat and Angie L. Cradock (2023) “Safe streets for some: A review of local active transportation responses across the U.S. during the COVID-19 pandemic”, Journal of Transport & Health, 30, p. 101603. Available at: 10.1016/j.jth.2023.101603.

research report

CARMEN Project 6: PNT with Signals of Opportunity and Real-World Jammed and Spoofed Environments

Publication Date

November 30, 2023

Author(s)

Zak Kassas

Areas of Expertise

Suggested Citation
Zak Kassas (2023) CARMEN Project 6: PNT with Signals of Opportunity and Real-World Jammed and Spoofed Environments. Final Report. CARMEN UTC. Available at: https://zenodo.org/doi/10.5281/zenodo.10256685 (Accessed: October 10, 2025).

published journal article

Using bilateral trading to increase ridership and user permanence in ridesharing systems

Transportation Research Part E: Logistics and Transportation Review

Suggested Citation
Neda Masoud, Roger Lloret-Batlle and R. Jayakrishnan (2017) “Using bilateral trading to increase ridership and user permanence in ridesharing systems”, Transportation Research Part E: Logistics and Transportation Review, 102, pp. 60–77. Available at: 10.1016/j.tre.2017.04.007.

working paper

Stochastic Dynamic Itinerary Interception Refueling Location Problem with Queue Delay for Electric Taxi Charging Stations

Abstract

A new facility location model and a solution algorithm are proposed that feature 1) itinerary-interception instead of flow-interception; 2) stochastic demand as dynamic service requests; and 3) queueing delay. These features are essential to analyze battery-powered electric shared-ride taxis operating in a connected, centralized dispatch manner. The model and solution method are based on a bi-level, simulation-optimization framework that combines an upper level multiple-server allocation model with queueing delay and a lower level dispatch simulation based on earlier work by Jung and Jayakrishnan. The solution algorithm is tested on a fleet of 600 shared-taxis in Seoul, Korea, spanning 603 km2, a budget of 100 charging stations, and up to 22 candidate charging locations, against a benchmark “naïve” genetic algorithm that does not consider cyclic interactions between the taxi charging demand and the charger allocations with queue delay. Results show not only that the proposed model is capable of locating charging stations with stochastic dynamic itinerary-interception and queue delay, butt that the bi-level solution method improves upon the benchmark algorithm in terms of realized queue delay, total time of operation of taxi service, and service request rejections. Furthermore, we show how much additional benefit in level of service is possible in the upper-bound scenario when the number of charging stations approaches infinity.

Suggested Citation
Jaeyoung Jung, Joseph Y.J. Chow, R. Jayakrishnan and Ji Young Park (2013) Stochastic Dynamic Itinerary Interception Refueling Location Problem with Queue Delay for Electric Taxi Charging Stations. Working Paper UCI-ITS-WP-13-2. Institute of Transportation Studies, Irvine, p. 28p. Available at: https://escholarship.org/uc/item/8xz102r3.

conference paper

The California ATMS Testbed Research Program: An Overview

Proceedings, IVHS America Annual Conference

Publication Date

January 1, 1995

Author(s)

Suggested Citation
Wilfred W. Recker (1995) “The California ATMS Testbed Research Program: An Overview”, in Proceedings, IVHS America Annual Conference. Washington, D. C..