research report

Implementation of a Tool for Measuring ITS Impacts on Freeway Safety Performance

Abstract

The research was undertaken to develop a tool for assessing the impacts of changes in freeway traffic flow on the level of traffic safety. Safety is measured in terms of the probability of a reportable accident, and the tool is so far restricted to urban freeway mainlines with substantial traffic levels. The tool will: (1) monitor the safety level of freeway operations (2) aid in freeway planning. The tool was calibrated by applying advanced statistical models to actual data combined from two sources: Vehicle Detector Station (VDS) data for freeways in Orange County (District 12), and data on all reported accidents in Orange County from the Traffic Surveillance and Analysis System (TASAS). The analytical engine that drives the safety tool is based on models that are highly effective in identifying those myriad aspects of traffic flow that are statistically related to accident probabilities. It is recommended that Caltrans invest in projects that will validate the current work, and subsequently: (1) improve the accuracy of the safety predictions; (2) extend the applicability of the modeling approach to other Caltrans districts; and (3) evaluate the dissemination of safety predictions in real time.

Suggested Citation
Thomas F. Golob, James Marca and Will Recker (2007) Implementation of a Tool for Measuring ITS Impacts on Freeway Safety Performance. Final Report UCB-ITS-PRR-2007-9. Institute of Transportation Studies, Irvine, p. 76p. Available at: https://escholarship.org/uc/item/2nn3j1sd.

conference paper

An Integrated Transportation-Power System Model for a Decarbonizing World

Transportation Research Board 103rd Annual Meeting

Publication Date

January 1, 2024

Author(s)

Matthew Dean, Krishna Murthy Gurumurthy, Zhi Zhou, öMer Verbas, Taner Cokyasar, Kara Kockelman
Suggested Citation
Matthew D. Dean, Krishna Murthy Gurumurthy, Zhi Zhou, Omer Verbas, Taner Cokyasar and Kara Kockelman (2024) “An Integrated Transportation-Power System Model for a Decarbonizing World”. Transportation Research Board 103rd Annual Meeting.

published journal article

Land-use influences on trip-chaining in Portland, Oregon

Proceedings of the Institution of Civil Engineers - Urban Design and Planning

Publication Date

June 1, 2008
Suggested Citation
M.J. Greenwald and M.G. McNally (2008) “Land-use influences on trip-chaining in Portland, Oregon”, Proceedings of the Institution of Civil Engineers - Urban Design and Planning, 161(2), pp. 61–73. Available at: 10.1680/udap.2008.161.2.61.

working paper

Travel and Activity Participation as Influenced by Car Availability and Use

Publication Date

August 1, 1995

Associated Project

Author(s)

Thomas Golob, Mark Bradley, John W. Polak

Working Paper

UCI-ITS-WP-95-26, UCI-ITS-AS-WP-95-3

Areas of Expertise

Abstract

The objective of the research described in this paper is to determine how the use of specific modes of travel affects the relationships between out-of-home activity duration and the travel required for such activities. We proceed by constructing a model that interrelates classes of out-of-home activities and the travel required to participate in these activities, all as a function of population sociodemographic characteristics and the modes of travel used by the population. 

Suggested Citation
Thomas F. Golob, Mark A. Bradley and John W. Polak (1995) Travel and Activity Participation as Influenced by Car Availability and Use. Working Paper UCI-ITS-WP-95-26, UCI-ITS-AS-WP-95-3. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/47q6810f.

published journal article

Techno-economic and environmental analysis of clean hydrogen deployment: A case study of Los Angeles International Airport

Energy Conversion and Management

Publication Date

September 15, 2025

Author(s)

Sajjad Rezaei, Khaled Alsamri, Elio Simeoni, Jacqueline (Jacquie) Huynh, Jack Brouwer

Abstract

The primary strategy for addressing environmental concerns related to global aviation emissions is transitioning to low-carbon propulsion technologies. Hydrogen (H2) offers significant potential as a sustainable fuel, with anticipated zero to low carbon emissions. This study develops a methodological framework that integrates on-site electrolytic H2 production, storage, and transportation for airport applications. For the first time, the techno-economic feasibility of supplying clean liquid hydrogen (LH2) to Los Angeles International Airport (LAX) to support its transition toward sustainable operations by 2050 is comprehensively analyzed. The results underscore the critical role of integrating long-term H2 storage and short-term battery storage solutions to establish a reliable, self-sustained microgrid system at LAX. The estimated levelized cost of hydrogen (LCOH) ranges from $6.77 to $7.10 per kilogram of H2 in 2030, decreasing significantly to approximately $3.78 per kilogram of H2 by 2050, showing the viability of deploying clean H2 at LAX. Additionally, this study, for the first time, quantifies the global warming potential (GWP) of clean H2 supply pathways for airport applications, revealing a range of 0.29 to 0.35 kg CO2-eq/kg H2 by 2050, with H2 venting from electrolysis identified as the dominant contributor. The findings emphasize the feasibility of H2 as a sustainable aviation fuel and provide actionable strategies for its implementation at LAX. This work advances the hydrogen aviation field by bridging the gap between the general clean H2 supply chain strategies and the specific needs of the aviation sector, thereby contributing to California’s ambitious climate goals. Future research is recommended to address limitations in cost optimization, lifecycle impacts, policy incentives, and safety innovations, enabling the scalable and practical implementation of H2 as a sustainable aviation fuel at airports.

Suggested Citation
Sajjad Rezaei, Khaled Alsamri, Elio Simeoni, Jacqueline Huynh and Jack Brouwer (2025) “Techno-economic and environmental analysis of clean hydrogen deployment: A case study of Los Angeles International Airport”, Energy Conversion and Management, 340, p. 119946. Available at: 10.1016/j.enconman.2025.119946.

published journal article

Markovian real-time adaptive control of signal systems

Mathematical and Computer Modelling

Abstract

An approach to real-time control of a network of signalized intersections is proposed based on a discrete time, stationary, Markov control model (also known as Markov decision process or Markov dynamic programming). The approach incorporates microscopic simulation of actuated controller output signals in response to probabilistic forecasts of individual vehicle actuations at downstream inductance loop detectors derived from a macroscopic link transfer function. An Artificial Neural Network representation of vehicle delay estimations is proposed and tested for approximate real-time evaluation of potential traffic signal transitions at three-second evaluation intervals. A series of off-line tests of the developed procedures are applied to a simplified network of five intersections; these tests provide promising indications of this approach.

Suggested Citation
W.W. Recker, B.V. Ramanathan, X.-H. Yu and M.G. McNally (1995) “Markovian real-time adaptive control of signal systems”, Mathematical and Computer Modelling, 22(4-7), pp. 355–375. Available at: 10.1016/0895-7177(95)00144-q.

Phd Dissertation

Graph Neural Network for Integrated Circuits and Cyber-Physical Systems Security

Publication Date

January 1, 2023

Author(s)

Abstract

This Ph.D. dissertation presents a comprehensive investigation into addressing security and reliability challenges in embedded and Cyber-Physical Systems (CPS). Our research leverages advanced machine learning techniques such as Graph Neural Networks (GNN) to develop novel methodologies for cross-layer security analysis.This dissertation addresses the growing risk posed by the globalization of the Integrated Circuit (IC) supply chain, whereby the majority of the design, fabrication, and testing processes have been outsourced to untrusted third-party entities across the globe. This development has significantly increased the threat of malicious modifications, known as Hardware Trojans (HTs), being inserted into Third-Party Intellectual Property (3PIP). HTs pose a substantial risk to IC integrity, functionality, and performance. Despite numerous HT detection methods proposed in existing literature, most limitations include reliance on a golden reference circuit, lack of generalizability, limited detection scope, low localization resolution, and manual feature extraction and property definition. Furthermore, the equally important task of HT localization has been neglected. This research proposes an innovative, golden reference-free method for HT detection and localization at the pre-silicon stage of IC development, employing models based on GNN. The circuit design is converted into a graph that is an intrinsic data structure for hardware design and captures the computational structure and data dependencies. We develop a graph classification model to distinguish between HT-free and circuits infected with known or even unknown HTs. To push the boundaries further, we extract node attributes from the HDL code and devise a Graph Convolutional Network (GCN) that facilitates automatic feature extraction, enabling the classification of nodes as either Trojan or benign. This methodology offers an automated approach to HT detection and localization, relieving designers of the need for time-consuming manual code review. The developed method achieves exceptional performance in detecting HT-infected circuits and locating the HT. The approach outlined in this dissertation sets a new benchmark for HT detection and localization, offering a scalable, efficient, and highly accurate tool for securing the pre-silicon IC supply chain.This dissertation expands to encompass the challenges facing IP piracy. The productivity gap, coupled with time-to-market pressure, has led to increased interest in hardware Intellectual Property (IP) core design within the semiconductor industry, dramatically reducing design and verification costs. Recognizing these challenges, this dissertation proposes a novel IP piracy detection methodology, modeling circuits and assessing similarity between IP designs. Contrary to traditional methods that embed a signature within the circuit design, our method does not introduce additional hardware overhead, nor is it vulnerable to removal, masking, or forging attacks. This approach effectively exposes IP infringements, even when the original IP is complicated by the adversary to deceive the IP owner. To represent the circuit accurately for modeling, we translate the hardware design into a data-flow graph due to similar data types and properties and subsequently model it using state-of-the-art graph learning methods. This approach effectively complements the GNN-based techniques proposed earlier in this dissertation, presenting a robust and comprehensive suite of solutions for security and reliability challenges in the semiconductor industry. Moving to the CPS domain, the dissertation addresses security challenges in IoT systems through the development of adaptive anomaly detection methods. The first proposed approach utilizes IoT sensor data and fog computing to ensure data integrity and detect anomalous incidents. The proposed methodology incorporates our sensor association algorithm, LSTM neural networks, and Gaussian estimation for real-time anomaly detection. The dissertation further extends the research to multi-modal data fusion, where the integration of sensor and communication data using GNN enables improved anomaly detection, source identification, and recovery in IoT systems.Overall, this dissertation showcases the application of advanced techniques such as GNN and machine learning in enhancing security and reliability in hardware design and IoT systems. The proposed methodologies for anomaly detection, hardware Trojan detection, IP piracy detection, and cross-layer security analysis contribute to advancing the state-of-the-art in ensuring the integrity and security of critical systems in the digital era.

Suggested Citation
Rosin Yasaei (2023) Graph Neural Network for Integrated Circuits and Cyber-Physical Systems Security. PhD Dissertation. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/u4evf/cdi_proquest_journals_2854332836.

published journal article

Free transit for students to regain ridership: Users and boarding characteristics of LA Metro's GoPass program

Journal of Transport Geography

Publication Date

December 1, 2025

Abstract

The Los Angeles County Metropolitan Transportation Authority (LA Metro) started in October 2021 the largest free transit pass program in the U.S. to date. Known as GoPass, it serves students from kindergarten to community colleges in Los Angeles County, the most populated county in the U.S. Although many free transit pass programs have been created, few have been analyzed from the point of view of transit agencies (i.e., for the characteristics of their users and their impact on ridership). To address this gap, we first examine GoPass’ contribution to LA Metro’s bus boardings, before comparing selected characteristics of the students enrolled in GoPass in 2023 with census data. We find some opportunities for additional growth, including for female students. To understand GoPass usage, we estimated a generalized spatial regression model that explains annual GoPass boardings aggregated by census tract (detailed usage data are unavailable to protect the students’ privacy) using a broad range of socioeconomic and built environment variables. Our results confirm the presence of strong spatial effects. We find that census tracts with more young males, more transit stops, mixed land use, and more participating schools accessible within 30 min by transit have more GoPass boardings. Conversely, the number of GoPass boardings decreases with more access to private vehicles, property crimes, multifamily units, and a higher population density. A better understanding of the characteristics of GoPass users and GoPass usage is useful to improve GoPass and to inform transit agencies interested in creating similar programs.

Suggested Citation
Farzana Khatun and Jean-Daniel Saphores (2025) “Free transit for students to regain ridership: Users and boarding characteristics of LA Metro's GoPass program”, Journal of Transport Geography, 129, p. 104442. Available at: 10.1016/j.jtrangeo.2025.104442.

published journal article

The political economy of urban transport-system choice

Journal of Public Economics

Publication Date

August 1, 2006

Author(s)

Jan Brueckner, Harris Selod
Suggested Citation
Jan K. Brueckner and Harris Selod (2006) “The political economy of urban transport-system choice”, Journal of Public Economics, 90(6-7), pp. 983–1005. Available at: 10.1016/j.jpubeco.2005.06.004.