working paper

A Property Rights Framework for Transit Services

Publication Date

December 1, 1995

Author(s)

Daniel B. Klein, Adrian Moore

Working Paper

UCI-ITS-WP-95-22, UCTC 303

View working paper

Abstract

The paper shows how variations in systems of property rights explain diverse experiences of urban jitneys and buses. Scheduled bus service entails route specific investments and cultivation of a market. If these investments can be expropriated by interloping jitneys, scheduled service will be dissolved. Property rights in curbspace determine whether scheduled service will be preserved, and whether jitney services will co-exist. We analyze the dynamics of thick and thin transit markets, with and without curb rights. We develop a governance system of curb rights that would let bus operators appropriate their own investments in scheduled service, yet would avoid monopoly by letting jitneys and competing scheduled services operate along the same route. A property rights system dispenses with government ownership, franchise contracting, and regulation.

Suggested Citation

Daniel B. Klein and Adrian T. Moore (1995) A Property Rights Framework for Transit Services. Working Paper UCI-ITS-WP-95-22, UCTC 303. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/36f657t2.

research report

Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach

Publication Date

April 1, 2019

Associated Project

Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach

Author(s)

Wenlong Jin, Adrià Morales Fresquet

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience Intelligent Transportation Systems, Emerging Technologies, & Big Data

View research report

Abstract

Numerical simulations have shown that the network fundamental diagram (NFD) of a signalized network is significantly affected by the green ratio. An analytical approximation of the NFD has been derived from the link transmission model. However, the consistency between these approaches has not been established, and the impacts of other factors are still unrevealed. This research evalutes the impacts of start-up and clearance behaviors in a signalized network from a network fundamental diagram approach. Microscopic simulations based on Newell’s car-following model are used for testing the bounded acceleration (start-up) and aggressiveness (clearance) effects on the shape of the NFD in a signalized ring road. This new approach is shown to be consistent with theoretical results from the link transmission model, when the acceleration is unbounded and vehicles have the most aggressive clearance behaviors. This consistency validates both approaches; but the link transmission model cannot be easily extended to incorporate more realistic start-up or clearance behaviors. With the new approach, this project demonstrates that both bounded acceleration and different aggressiveness lead to distinct network capacities and fundamental diagrams. In particular, they lead to start-up and clearance lost times of several seconds; and these lost times are additive. Therefore, the important role that these behaviors play in the NFD shape is studied to reach a better understanding of how the NFD responds to changes. This will help with designing better start-up and clearance behaviors for connected and autonomous vehicles.

Suggested Citation

Wen-Long Jin and Adrià Morales Fresquet (2019) Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach. Final Report. Available at: https://escholarship.org/uc/item/36v9c2ct (Accessed: October 11, 2023).

Related Publications

policy brief | Apr 2019

Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach

Phd Dissertation

Zero Emission Shared-Use Autonomous Vehicles: A Deployment Construct and Associated Energy Grid and Environmental Impacts

Publication Date

December 31, 2019

Author(s)

Van Wifvat

Areas of Expertise

Public Transit, Shared Mobility, & Active Transportation Zero-Emission Vehicles & Low-Carbon Fuels

View Phd Dissertation

Abstract

For decades, the leading cause of death for American youth has been the car accident, and the largest source of domestic Greenhouse Gas (GHG) and many Criteria Air Pollutants (CAPs) has been the transportation sector. The advent of the autonomous vehicle in combination with Battery-Electric Vehicles (BEVs) and Fuel-Cell Electric Vehicles (FCEVs) presents an opportunity to transcend both pernicious challenges. In particular, the evolution of safer and more efficient autonomous (i.e., robotic) driving behavior via vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication, increased use of electric vehicles, and greater access to affordable and convenient shared (i.e., pooled) rides portend societal benefits including a significant reduction in energy demand and associated pollution. This dissertation evaluates the impact of Shared Autonomous Electric Vehicles (SAEVs, “Saves”) on the California energy grid, GHG emissions, and CAPs. Vehicle-centric impacts (i.e., efficiency changes due to vehicle design and driving behavior) are measured using a vehicle design tool together with a microscopic traffic simulation model to (1) design prototype SAEVs, and (2) measure their energy efficiency for standard and eco-driving scenarios and an array of performance characteristics (e.g., different electric drivetrains, various communication protocols, etc.). Fleet-centric impacts (i.e., changes to vehicle allocation and usage) are measured using ArcGIS with a Caltrans travel demand model dataset to allocate and size SAEV stations, where SAEVs recharge/refuel and are sent to serve nearby trips in a hypothetical SAEV-deployment construct. The Holistic Energy Grid modelling tool (HiGRID) is used to measure SAEV impacts on the California electric grid and grid GHG and CAPs. The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model (GREET) is used to measure corresponding transportation sector GHG and CAP impacts. Vehicle-centric energy impacts from SAEV-enabled eco-driving and platooning averaged net efficiency improvements of approximately 6-18%. Fleet-centric impacts include VMT changes from -11% to +36%, largely depending on ridesharing. Depending on SAEV design and operation, over 375,000 metric tons of annual CO2-equivalent GHG emissions could be reduced by adopting the proposed SAEV-deployment construct in lieu of the projected conventionally-driven vehicle fleet. Corresponding CAP impacts include a net reduction of over 250 metric tons of annual NOx emissions.

Suggested Citation

VAN THOMAS WIFVAT (2019) Zero Emission Shared-Use Autonomous Vehicles: A Deployment Construct and Associated Energy Grid and Environmental Impacts. PhD Dissertation. UC Irvine. Available at: https://escholarship.org/uc/item/5398t15h.

conference paper

Effective and light-weight deobfuscation and semantic-aware attack detection for PowerShell scripts

Proceedings of the 2019 ACM SIGSAC conference on computer and communications security

Publication Date

November 1, 2019

Author(s)

Zhen Li, Qi Alfred Chen, Chunlin Xiong, Yan Chen, Tiantian Zhu, Hai Yang

View conference paper

Abstract

In recent years, PowerShell is increasingly reported to appear in a variety of cyber attacks ranging from advanced persistent threat, ransomware, phishing emails, cryptojacking, financial threats, to fileless attacks. However, since the PowerShell language is dynamic by design and can construct script pieces at different levels, state-of-the-art static analysis based PowerShell attack detection approaches are inherently vulnerable to obfuscations. To overcome this challenge, in this paper we design the first effective and light-weight deobfuscation approach for PowerShell scripts. To address the challenge in precisely identifying the recoverable script pieces, we design a novel subtree-based deobfuscation method that performs obfuscation detection and emulation-based recovery at the level of subtrees in the abstract syntax tree of PowerShell scripts. Building upon the new deobfuscation method, we are able to further design the first semantic-aware PowerShell attack detection system. To enable semantic-based detection, we leverage the classic objective-oriented association mining algorithm and newly identify 31 semantic signatures for PowerShell attacks. We perform an evaluation on a collection of 2342 benign samples and 4141 malicious samples, and find that our deobfuscation method takes less than 0.5 seconds on average and meanwhile increases the similarity between the obfuscated and original scripts from only 0.5% to around 80%, which is thus both effective and light-weight. In addition, with our deobfuscation applied, the attack detection rates for Windows Defender and VirusTotal increase substantially from 0.3% and 2.65% to 75.0% and 90.0%, respectively. Furthermore, when our deobfuscation is applied, our semantic-aware attack detection system outperforms both Windows Defender and VirusTotal with a 92.3% true positive rate and a 0% false positive rate on average.

Suggested Citation

Zhenyuan Li, Qi Alfred Chen, Chunlin Xiong, Yan Chen, Tiantian Zhu and Hai Yang (2019) “Effective and light-weight deobfuscation and semantic-aware attack detection for PowerShell scripts”, in Proceedings of the 2019 ACM SIGSAC conference on computer and communications security. ACM, pp. 1831–1847. Available at: 10.1145/3319535.3363187.

conference paper

Forecasting network traffic for small and medium-sized communities using path flow estimator

Proceedings of the 85th annual meeting of the transportation research board

Publication Date

January 1, 2006

Author(s)

Will Recker, Piya Chootinan, Anthony Chen, Ming-Sheng Lee

Abstract

The objective of this study is to propose an alternative methodology to model and forecast network traffic for planning applications in small and medium-sized communities where resources debilitate the development and applications of 4-step models. The major thrust of the proposed approach is that model estimation and forecasting are each accomplished through an O-D estimation using the Path Flow Estimator that allows for the use of various planning and field data such as land uses (converted to zonal trip production and attraction), traffic counts, and target O-D table as estimation constraints. The proposed procedure is applied with empirical data from a small community, the City of St. Helena in California to demonstrate how it can be implemented in practice.

Suggested Citation

Wilfred W. Recker, Piya Chootinan, Anthony Chen and Ming S. Lee (2006) “Forecasting network traffic for small and medium-sized communities using path flow estimator”, in Proceedings of the 85th annual meeting of the transportation research board, p. 12p.

conference paper

Severity of accidents based on truck body classification

Proceedings of the 2013 summer research symposium, UC irvine

Publication Date

August 1, 2013

Author(s)

Alma Carillo, Sarah Hernandez, Stephen Ritchie

Suggested Citation

Alma Carillo, S. Hernandez and S.G. Ritchie (2013) “Severity of accidents based on truck body classification”, in Proceedings of the 2013 summer research symposium, UC irvine.

published journal article

A joint household travel distance generation and car ownership model

Transportation Research Part B: Methodological

Publication Date

December 1, 1989

Author(s)

Thomas Golob, Leo J. G. van Wissen

View published journal article

Suggested Citation

Thomas F. Golob and Leo van Wissen (1989) “A joint household travel distance generation and car ownership model”, Transportation Research Part B: Methodological, 23(6), pp. 471–491. Available at: 10.1016/0191-2615(89)90045-3.

published journal article

Accessibility of neotraditional neighborhoods: A review of design concepts, policies, and recent literature

Transportation Research Part A: Policy and Practice

Publication Date

March 1, 1995

Author(s)

Sherry Ryan, Michael McNally

View published journal article

Abstract

Neotraditional neighborhood design (NTND) has gained increasing attention from professional, academic and popular circles during the past 10 years. This review establishes a baseline evaluation of NTND, with the goal of providing the background for more specific research in the future. The first section of the article orients NTND in a historical context, reviewing the main subdivision design trends of the past century and how NTND has either diverged or borrowed from them. The second section focuses on a review of current issues and policies related to this planning trend, with special attention directed toward transportation and land use research and the effect of neotraditional design on accessibility of the transportation system. The article concludes by offering an assessment of the potential of NTND to address growth-related problems in suburban areas and by identifying key unmet research needs.

Suggested Citation

S. Ryan and M.G. McNally (1995) “Accessibility of neotraditional neighborhoods: A review of design concepts, policies, and recent literature”, Transportation Research Part A: Policy and Practice, 29(2), pp. 87–105. Available at: 10.1016/0965-8564(94)e0008-w.

published journal article

The Association Between Ambient Fine Particulate Matter and Spontaneous Preterm Birth: Evidence From a Large Pregnancy Cohort in Southern California [ID 1244]

Obstetrics & Gynecology

Publication Date

June 1, 2025

Author(s)

Alexa N. Reilly, Anqi Jiao, Tarik Benmarhnia, Yi Sun, Chantal Avila, Jun Wu

Areas of Expertise

Safety, Public Health, & Mobility Justice

View published journal article

Abstract

INTRODUCTION: Although studies have found positive associations between exposure to PM2.5 and preterm birth, distinguishing between spontaneous preterm birth (sPTB) and iatrogenic preterm birth (iPTB) was a challenge in previous research. This study examined associations between total PM2.5 and PM2.5 constituent exposure and sPTB. METHODS: This is a retrospective cohort study from 2008 to 2018 of singleton live births within a large health care system in southern California, United States. Daily total PM2.5 concentrations and monthly data on five PM2.5 constituents (sulfate, nitrate, ammonium, organic matter, and black carbon) were obtained. The average concentrations of total PM2.5 and constituents were calculated over the pregnancy and by trimester. A novel natural language processing algorithm was used to identify sPTB in medical records. Discrete-time survival models were used to estimate the associations of total PM2.5 and constituents with sPTB. Effect modifiers included maternal race/ethnicity, educational attainment, household income, and green space. RESULTS: There were 19,341 (4.7%) sPTBs among 409,037 births. We observed significant associations of sPTB with PM2.5, black carbon, nitrate, and sulfate. The second trimester was the most susceptible window. Significantly higher associations with PM2.5 were observed among mothers with lower educational attainment, lower income, and less green space exposure. CONCLUSIONS/IMPLICATIONS: Maternal exposures to PM2.5 and specific PM2.5 constituents were associated with an increased risk of sPTB. Mothers with lower socioeconomic status were vulnerable, whereas green space was a protective effect modifier.

Suggested Citation

Alexa N. Reilly, Anqi Jiao, Tarik Benmarhnia, Yi Sun, Chantal Avila and Jun Wu (2025) “The Association Between Ambient Fine Particulate Matter and Spontaneous Preterm Birth: Evidence From a Large Pregnancy Cohort in Southern California [ID 1244]”, Obstetrics & Gynecology, 145(6S), p. 40S. Available at: 10.1097/AOG.0000000000005917.037.

book/book chapter

Methodological developments in activity-travel behavior analysis

Publication Date

January 1, 2012

Author(s)

David Brownstone

Suggested Citation

David Brownstone (2012) “Methodological developments in activity-travel behavior analysis”, in C.R.B. R. M. Pendayala (ed.) Travel behavior research in an evolving world. International Association for Travel Behavior Research, pp. 249–260.