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Open Access Publications from the University of California

California PATH is a unique research organization. It focuses on solving California's and the nation's transportation problems by conducting relevant and high-quality research that advances the state of the art. The research is performed by a statewide group of faculty, graduate students, and research staff of diverse backgrounds and expertise working closely together. At the same time, PATH produces the next generation of leaders in academia and the transportation profession. PATH's ongoing research directly addresses the mobility, reliability, and safety goals of our Caltrans (California Department of Transportation) partners and will place major emphasis on field testing of the most promising strategies for traffic control, traveler information, intersection safety, transit, and other mobility options.

Alexander Skabardonis, Adjunct Professor of Civil and Environmental Engineering and Research Engineer at the Institute of Transportation Studies, is PATH's director.

Cover page of Reduce Emissions and Improve Traffic Flow Through Collaborative Autonomy

Reduce Emissions and Improve Traffic Flow Through Collaborative Autonomy

(2024)

This report explores opportunities for employing autonomous driving technology to dampen stop-and-go waves on freeways. If successful, it could reduce fuel consumption and emissions. This technology was tested in an on-road experiment with 100 vehicles over one week. Public stakeholders were engaged to assess the planning effort and feasibility of taking the technology to the next level: a pilot involving 1000+ vehicles over several months. Considerations included the possible geographical boundaries, target fleets of vehicles, and suitable facilities such as bridges or managed lanes. Flow smoothing technology may improve the user experience and operations of managed lanes or bridges, however it may require external incentives such as reduced tolls to entice the traveling public to use it. This must be matched with other goals such as verifying vehicle occupancy. It might be possible for some hybrid solution that addresses both challenges to provide a way forward. A concept of operations needs to be developed specifically for a target road geometry and a California partner. This concept should benefit from lessons learned from previous pilot projects and will need to be defined so as to achieve both (1) a penetration rate sufficient to achieve measurable effects; and (2) sufficient quality and quantity of data to confirm benefits.

Cover page of Connected Corridors: I-210 Aimsun Microsimulation Model

Connected Corridors: I-210 Aimsun Microsimulation Model

(2024)

This document provides a description of the Aimsun Next model that was developed for the I-210 Pilot Integrated Corridor Management (ICM) System.

Cover page of TMDD Standards Update Recommendations – Data Structures

TMDD Standards Update Recommendations – Data Structures

(2023)

This document provides a set of recommendations for modernization of the Traffic Management Data Dictionary (TMDD) (1), currently at version 3.1. These recommendations are based upon the following: Connected Corridors project experience; three previous technical memorandums provided under this project discussing the current and future state of transportation, the state of the supporting technology for information exchange, and a review of the TMDD standard; a gap analysis based on the three technical memorandums delivered as part of this project. The intention of this document is to inform the Institute of Transportation Engineers (ITE) committee responsible for TMDD, the California Department of Transportation (Caltrans), and users of the standard of potential improvements in the standard that should improve its ability to serve current and future transportation and traffic management needs

Cover page of Modernization of Center-to-Center Data Communication Standards: Sample Implementation Administration and User Guide

Modernization of Center-to-Center Data Communication Standards: Sample Implementation Administration and User Guide

(2021)

This document provides a guide to the reference sample application developed under the Traffic Management Data Dictionary (TMDD) modernization contract. The application provides a sample implementation of a SOAP implementation using the XML Schema Definition (XSD) and Web Service Description Language (WSDL) developed under the contract. In addition, it provides a sample implementation of a Kafka/JSON based messaging implementation. Both implementations utilize a sample set of data captured during the I-210 Connected Corridors contract. The application is intended for use by experienced Information Technology (IT) personnel as an example of both SOAP and Kafka implementations of a Center-to-Center (C2C) information exchange system.

Cover page of Modernization of Center-to-Center Data Communication Standards: Gap Analysis Technical Memorandum

Modernization of Center-to-Center Data Communication Standards: Gap Analysis Technical Memorandum

(2021)

This document provides a gap analysis based on three previous technical memorandums delivered as part of this project, including a review of the Traffic Management Data Dictionary (TMDD) standard, a review of current and future transportation needs, and a review of the state of the art in technology and systems development. The intention of this document is to provide a review of this standard for transmission of data between traffic management centers (TMCs), with explicit commentary on usability of the standard with specific examples based on its implementation in the Caltrans I-210 Connected Corridors program.

Cover page of TMDD Standards Review Technical Memorandum

TMDD Standards Review Technical Memorandum

(2021)

This document presents a review of the Traffic Management Data Dictionary (TMDD) standard, specifically version 3.03d with some analysis of the newest version 3.1, released in January 2020. The intention of this document is to provide a review of this standard for transmission of data between traffic management centers (TMCs), with specific commentary on usability of the standard with specific examples based on its implementation in the Caltrans I-210 Connected Corridors program. TMDD is published by the Institute of Transportation Engineers (ITE), an international organization of transportation engineers and the American Association of State Highway and Transportation Officials (AASHTO), an organization of highway and transportation officials in the United States with members from all 50 states, the District of Columbia, and Puerto Rico. The standard is provided in two parts, along with a reference guide, providing guidance for those developing, procuring, or implementing systems that communicate traffic and transportation device information between or within traffic management centers (TMCs). This includes information regarding system requirements, interface design, communication methods, as well as data schema and definitions.

Cover page of Current and Future Transportation Management High-Level Requirements Technical Memorandum

Current and Future Transportation Management High-Level Requirements Technical Memorandum

(2021)

This document presents a review of the current and future requirements for information exchange between traffic management centers, with emphasis on the changes expected due to the changing nature of transportation and the advances in technology that are becoming prevalent in the transportation ecosystem. The intent of this document is to provide a look at the source of changes required within center-to-center communication and new requirements that will need to be addressed as transportation undergoes significant change due to new transportation modes, technology advances in connected and automated vehicles, advances in infrastructure elements, and other changes that are expected in the future.

Cover page of TMDD Standards Update Recommendations – Data and System Security

TMDD Standards Update Recommendations – Data and System Security

(2021)

This document provides recommendations for modifications to the current TMDD standard. Its goal is to provide a foundation for modernizing the standard. This document specifically provides recommendations for implementing this project’s gap analysis recommendations related to providing security guidance for each approved transmission protocol. Included in this document are recommendations related to a new volume of the specification dealing with minimum security requirements and security recommendations for each data transmission protocol.

Cover page of Bus Lanes/Bus Rapid Transit Systems on Highways: Review of the Literature

Bus Lanes/Bus Rapid Transit Systems on Highways: Review of the Literature

(2009)

This report presents the findings of a study of commercial motor vehicle inspection and screening station practices with a focus on the use of various technologies to help address problems related to safety, security, roadway infrastructure, and air quality. A review of industry literature identified the various types of inspection and screening practices that have been and are being implemented including weight and size management, on-board equipment checking, driver-related violations and cargo monitoring, credential checking, and exhaust emissions monitoring. The review also identified technologies that have been employed as part of these practices as well as an assessment of their performance. The research also involved the use of a survey of State and Provincial Departments of Transportation in North America that have implemented specific practices. Survey findings indicate that to a certain degree a more integrated and multi-practice approach is being taken; a wide array of technologies is in use; and, technology evaluations show they have generally performed well.

Cover page of The Naturalistic Driver Model: Development, Integration, and Verification of Lane Change Maneuver, Driver Emergency and Impairment Modules

The Naturalistic Driver Model: Development, Integration, and Verification of Lane Change Maneuver, Driver Emergency and Impairment Modules

(2008)

This report documents work conducted in order to support the development of a driver model. This work consisted of (i) a review of driver models for identifying the possibility to add some functionalities to the current model based on existing models and (ii) the data collection and analysis in order to describe the mechanism of distraction and potentially offer some quantification of its effect on drivers’ behavior and performance.