working paper

A Simultaneous Model of Activity Participation and Trip Chain Generation by Households

Publication Date

June 30, 1997

Author(s)

Thomas Golob

Areas of Expertise

Travel Behavior, Land Use, & the Built Environment

View working paper

Abstract

A trip generation model has been developed using a time-use perspective, in which trips are generated in conjunction with out-of-home activities, and time spent traveling is another component of overall time use. The model jointly forecasts three sets of endogenous variables – (1) activity participation and (2) travel time (together making up total out-of home time use), and (3) trip generation — as a function of household characteristics and accessibility indices. It is estimated with data from the Portland, Oregon 1994 Activity and Travel Survey. Results show that the basic model, which has ten endogenous time use and trip generation variables and thirteen exogenous variables, fits well, and all postulated relationships are upheld. Test show that the basic model, which divides activities into work and nonwork, can be extended to a three-way breakdown of subsistence, discretionary and obligatory activities. The model can also capture the effects of in-home work on trip chaining and activity participation. We use the model to explore the effects on time use and trip chaining of GIS-based and zone-based accessibility indices.

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Project Evaluation

Phd Dissertation

A network traffic control algorithm with analytically embedded traffic flow models

Publication Date

June 29, 1997

Author(s)

Wann-Ming Wey

Areas of Expertise

Intelligent Transportation Systems, Emerging Technologies, & Big Data

View Phd Dissertation

Abstract

This dissertation documents the development of optimization models in a mixed integer-linear form for the control of network traffic signalized intersections. The existing network traffic signal optimization formulations usually do not include traffic flow models, except for control schemes such as SCOOT that use simulation for heuristic optimization. Other conventional models normally use isolated intersection optimization with traffic arrival prediction using detector information, or optimization schemes based on green bandwidth. In this dissertation a complete formulation of the problem that includes explicit constraints to model the movement of traffic along the streets between the intersections in a time-expanded network is presented, as well as constraints to capture the permitted movements from modern signal controllers. The platoon dispersion model used is the well-known Robertson’s model, which forms linear constraints. Thus it is a rare example of a traffic simulation being analytically embedded in an optimization formulation. The formulation is an integer-linear program, and does not assume fixed cycle lengths or phase sequences. It assumes full information on external inputs, but can be incorporated in a sensor-based environment. The integer-linear program formulation may not be efficiently solved with standard simplex and branch and bound techniques. We discuss network programming formulations to handle the linear platoon dispersion equations and the integer constraints at the intersections. A special purpose network simplex algorithm for fast solution is addressed in the proposed solution approach. The optimization model takes the form of mixed integer linear programming. The control strategies generated by these optimization models were compared with those derived from conventional signal timing models, using the TRAF-NETSIM microscopic simulation model. It was found that the optimization models successfully produced optimal signal timing plans for the various signalized intersections including simulated and real-world networks. The proposed optimization models consistently outperformed the conventional signal control methods with respect to system delay objective. This conclusion was drawn from the TRAF-NETSIM simulation.

Phd Dissertation

Network surveillance supported object-based and task-based time-bounded fault tolerance schemes and their incorporation into a timeliness-guaranteed kernel

Publication Date

June 29, 1997

Author(s)

Chittur Subbaraman

Areas of Expertise

Intelligent Transportation Systems, Emerging Technologies, & Big Data

View Phd Dissertation

Abstract

Real-time fault tolerance (RTFT) is a core technology for increasing the reliability of computer-based safety-critical applications such as space applications, factory automation systems, etc. In recent years, the real-time computing market has started showing explosive growth. In order to realize highly robust real-time fault tolerant computing stations, several component techniques are necessary. Among the most significant include (a) a scaleable RTFT scheme, (b) a network surveillance (NS) scheme, (c) a timeliness-guaranteed kernel that supports both the RTFT and the NS schemes. This dissertation attempts to make a significant step forward towards the goal of realizing ultra-reliable computer-based safety-critical systems. As a first step in this direction, the following new technologies have been devised: (i) the primary-shadow time-triggered message-triggered object (TMO) replication (PSTR) scheme which provides time-bounded recovery from faults in TMO structured systems, (ii) the supervisor-based network surveillance (SNS) scheme which is effective in a variety of point-to-point networks and is amenable to fault detection latency bound analysis. Second, it was observed that even though a few promising component technologies that addressed certain specific requirements of real-time fault tolerant computing stations have been established, little efforts were made to integrate these technologies. Only such integrated technologies can meet the diverse demands that are imposed by safety-critical applications. This dissertation attempts to establish guidelines for such integration. The following integrated schemes have been devised: (i) the PSTR scheme and the SNS scheme, (ii) the distributed recovery block (DRB) scheme established earlier and the SNS scheme, (iii) the adaptable DRB scheme established earlier and the SNS scheme. Third, convincing demonstrations of the validity and potential utility of the devised schemes would facilitate their use in real-world applications. A timeliness-guaranteed kernel developed earlier was extended to support all the devised schemes. A TMO-structured defense application supported by the newly extended kernel was also made fault-tolerant. Finally, the performance analyses of the RTFT and NS schemes, even though of great importance, have been scarcely practiced. We have analyzed the performance of the devised schemes and obtained some tight time bounds. The modeling and analysis techniques presented would serve as useful guides to system engineers.

Preprint Journal Article

A Choice Experiment Survey of Drayage Fleet Operator Preferences for Zero-Emission Trucks

Publication Date

January 1, 2025

Associated Project

Assessing Drayage Fleet Operator Attitudes and Practices Towards Purchasing Alternative Fuels Vehicles

Author(s)

Youngeun Bae, Stephen Ritchie, Craig Rindt

Areas of Expertise

Freight, Logistics, & Supply Chain Zero-Emission Vehicles & Low-Carbon Fuels

View Preprint Journal Article

Abstract

Many U.S. states are supporting the transition of the heavy-duty vehicle (HDV) sector to zero-emission vehicles (ZEVs), with California leading the way through its policy and regulatory initiatives. Within various HDV fleet segments, California’s drayage fleets face stringent targets, requiring all vehicles newly registered in the Truck Regulation Upload, Compliance, and Reporting System to be ZEVs starting January 2024, and all drayage trucks in operation to be zero-emission by 2035. Understanding fleet operator behavior and perspectives is crucial for achieving these goals; however, it remains a critical knowledge gap. This study investigates the preferences and influencing factors for ZEVs among drayage fleet operators in California. A stated preference choice experiment survey was conducted, developed based on previous qualitative studies and literature reviews. With participation from 71 fleets of various sizes and alternative fuel adoption status, there were 648 choice observations in a dual response design collected, consisting of a forced choice between ZEVs and a free choice between ZEVs and status quo alternatives. Multinomial logit model analyses revealed driving range and purchase costs as significant factors for ZEV adoption, with charging facility construction costs also critical in hypothetical choices between ZEVs and status quo alternatives. Fleet or organization size also influenced ZEV choices, with large fleets more sensitive to operating costs and small organizations more sensitive to off-site stations. These findings enhance understanding in this area and provide valuable insights for policymakers dedicated to facilitating the transition of the HDV sector to zero-emission.

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policy brief | February 05, 2025

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What are the Public Health and Environmental Implications of Drayage Truck Electrification Targets in California?

Publication Date

January 1, 2025

Associated Project

Simulation of Zero-Emissions Self-Driving Drayage Trucks in a Busy Freight Corridor

Author(s)

Jean-Daniel Saphores, Monica Ramirez-Ibarra

Areas of Expertise

Freight, Logistics, & Supply Chain Zero-Emission Vehicles & Low-Carbon Fuels

View policy brief

Abstract

To better understand the implications of transitioning drayage trucks to zero-emission, this project analyzed the health impacts and GHG freeway emissions from diesel-powered drayage trucks and the benefits of replacing them with zero-emission trucks, accounting for current and expected air quality regulations. The study area stretched between the San Pedro Bay and the Inland Empire, home to large warehouse complexes. It focused on two years: 2012 (when pre-2007 drayage trucks were phased out in the Clean Air Action Plan), and 2035 (the deadline in Executive Order N-79-20). The analyses incorporated projections of the size and composition of the vehicle fleets from data collected by the California Air Resources Board (CARB), estimates of future emission factors from the U.S. Environmental Protection Agency that account for projected technology improvements, and projected increases in cargo demand at the ports in 2035 compared to 2012.

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published journal article | February 03, 2025

Health and equity impacts from electrifying drayage trucks

Phd Dissertation | February 03, 2025

Electrification, Connectivity, & Active Demand Management: Addressing the traffic, health, and EJ impacts of drayage trucks in Southern California

Preprint Journal Article

Small and Large Fleet Perceptions on Zero-emission Trucks and Policies

Publication Date

January 1, 2025

Associated Project

California’s Zero-Emission Truck Goals and Policies: Implications for Small Drayage Fleets

Areas of Expertise

Freight, Logistics, & Supply Chain Zero-Emission Vehicles & Low-Carbon Fuels

View Preprint Journal Article

Abstract

Given that small fleets (defined as those with 20 or fewer vehicles) represent a considerable portion of the heavy-duty vehicle (HDV) sector, understanding their perspectives, along with those of large fleets, on zero-emission vehicles (ZEVs) and related policies is crucial for achieving the U.S. HDV sector’s ZEV transition goals. However, research focusing on small fleets or comparing both segments has been limited. Focusing on California’s drayage sector with stringent ZEV transition targets, this study investigates the awareness and perceptions of small and large fleet operators on ZEV technologies and policies established to promote ZEV adoption. Using a fleet survey, we obtained 71 responses from both small and large fleets. We employed a comprehensive exploratory approach, utilizing descriptive analysis, hypothesis testing, and thematic analysis. Findings reveal that both segments generally rated their ZEV knowledge as close to neutral, with about a third reporting limited awareness of the ZEV policy. Both segments highlighted various adoption barriers, including challenges with infrastructure, costs, and operational compatibility. Business strategies under the ZEV policy differed significantly: small fleets planned to delay or avoid ZEV procurement, with some considering relocation, while large fleets were more proactive, with many already having procured or preparing to procure ZEVs. Both segments voiced concerns about the disproportionate impact on small fleets. The findings enhance our understanding of equity issues in ZEV adoption across fleet segments and offer valuable insights for policymakers committed to a more equitable distribution of the impacts.

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Fleet Operator Perspectives on Alternative Fuels for Heavy-duty Vehicles

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published journal article

Quantifying the Employment Accessibility Benefits of Shared Automated Vehicle Mobility Services: Consumer Welfare Approach Using Logsums

Publication Date

October 5, 2020

Associated Project

Assessment of the Employment Accessibility Benefits of Shared Autonomous Mobility Services

Areas of Expertise

Intelligent Transportation Systems, Emerging Technologies, & Big Data Safety, Public Health, & Mobility Justice

View published journal article

Abstract

The goal of this study is to assess and quantify the potential employment accessibility benefits of shared-use automated vehicle (AV) mobility service (SAMS) modes across a large diverse metropolitan region considering heterogeneity in the working population. To meet this goal, this study proposes employing a welfare-based (i.e. logsum-based) measure of accessibility, obtained via estimating a hierarchical work destination-commute mode choice model. The employment accessibility logsum measure incorporates the spatial distribution of worker residences and employment opportunities, the attributes of the available commute modes, and the characteristics of individual workers. The study further captures heterogeneity of workers using a latent class analysis (LCA) approach to account for different worker clusters valuing different types of employment opportunities differently, in which the socio-demographic characteristics of workers are the LCA model inputs. The accessibility analysis results in Southern California indicate: (i) the accessibility benefit differences across latent classes are modest but young workers and low-income workers do see higher benefits than high- and middle-income workers; (ii) there are substantial spatial differences in accessibility benefits with workers living in lower density areas benefiting more than workers living in high-density areas; (iii) nearly all the accessibility benefits come from the SAMS-only mode as opposed to the SAMS+Transit mode; and (iv) the SAMS cost per mile assumption significantly impacts the magnitude of the overall employment accessibility benefits.

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Shared Autonomous Mobility Services Show Promise for Increasing Access to Employment in Southern California

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policy brief

Transportation Plans: Their Informational Content and Use Patterns in Southern California

Publication Date

June 29, 2018

Associated Project

Transportation Plans: Their Informational Content and Use Patterns in Southern California

Author(s)

Jae Hong Kim, Xiangyu Li, Tanjeeb Ahmed, Victor Paitimusa

Areas of Expertise

Travel Behavior, Land Use, & the Built Environment

View policy brief

Related Publications

policy brief | February 03, 2025

General Plan Content Related to Transportation and Land Use Varies Significantly Across Cities in Orange County

research report | February 03, 2025

Transportation Plans: Their Informational Content and Use Patterns in Southern California

policy brief

What Matters Most to Drayage Companies When Considering a Zero-Emission Truck: Insights from Small and Large Fleet Operators

Publication Date

January 1, 2025

Associated Project

Assessing Drayage Fleet Operator Attitudes and Practices Towards Purchasing Alternative Fuels Vehicles

Author(s)

Youngeun Bae, Stephen Ritchie, Craig Rindt

Areas of Expertise

Freight, Logistics, & Supply Chain Zero-Emission Vehicles & Low-Carbon Fuels

View policy brief

Abstract

Drayage trucks (i.e., heavy-duty trucks that move containers and bulk freight between ports and rail facilities, distribution centers, and other nearby locations) are a critical part of port operations, however, they also adversely affect air quality. In California, drayage fleets are facing strict regulatory pressure under the Advanced Clean Fleets (ACF) regulations. Starting in January 2024, all newly registered drayage trucks in the CARB Online System must be zero emission vehicles (ZEVs), so either a battery electric truck (BET) or hydrogen fuel cell electric truck (HFCET). By 2035, every drayage truck operating in California must be zero-emission.
To successfully meet this policy goal, it is important to understand the viewpoints of drayage fleet operators. However, there is limited knowledge about how fleets of various sizes, especially small fleets with 20 or fewer vehicles (which make up 70% of the sector), are responding to ZEVs and related policies. To bridge this gap, the study team surveyed both small and large drayage fleet operators at the Ports of Los Angeles and Long Beach, with 71 companies participating. As part of the survey, fleet operators were asked to choose a preferred truck under different scenarios. In the first scenario, they chose between different ZEV trucks; in the second scenario, they chose between ZEVs, diesel, or natural gas trucks, shedding light on potential reasons which fleets might delay ZEV adoption if they still prefer diesel or natural gas trucks. The team analyzed around 650 choice observations using statistical models to explore these preferences, as well as other survey items regarding their perceptions.

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Preprint Journal Article | February 28, 2025

A Choice Experiment Survey of Drayage Fleet Operator Preferences for Zero-Emission Trucks

published journal article

A vehicle ownership and utilization choice model with endogenous residential density

Publication Date

December 31, 2013

Author(s)

David Brownstone, Hao (Audry) Fang

Areas of Expertise

Travel Behavior, Land Use, & the Built Environment

View published journal article

Abstract

This paper explores the impact of residential density on households’ vehicle type and usage choices using the 2001 National Household Travel Survey (NHTS). Attempts to quantify the effect of urban form on households’ vehicle choice and utilization often encounter the problem of sample selectivity. Household characteristics that are unobservable to the researchers might determine simultaneously where to live, what vehicles to choose, and how much to drive them. Unless this simultaneity is modeled, any relationship between residential density and vehicle choice may be biased. This paper extends the Bayesian multivariate ordered probit and tobit model developed in Fang (2008) to treat local residential density as endogenous. The model includes equations for vehicle ownership and usage in terms of number of cars, number of trucks (vans, sports utility vehicles, and pickup trucks), miles traveled by cars, and miles traveled by trucks. We carry out policy simulations that show that an increase in residential density has a negligible effect on car choice and utilization, but slightly reduces truck choice and utilization. The largest impact we find is a -.4 arc elasticity of truck fuel use with respect to density. We also perform an out-of-sample forecast using a holdout sample to test the robustness of the model.

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research report | March 21, 2025