Policy

Staging at the Curb: Evaluating the Impacts of Shared Automated Vehicle Fleet Operations Under Curb Usage Restrictions

Bahk, Younghun
Hyland, Michael
Susan Shaheen
Wolfe, Brooke
Cohen, Adam
2026

Shared automated vehicle (SAV) ridehailing services are now operating in several metropolitan regions in the United States. While providing benefits, SAV services may exacerbate issues related to curb usage and vehicle kilometers traveled (VKT) in urban areas. The objective of this study is to provide guidance to cities by evaluating the impacts of SAVs’ short-term curb usage for staging between serving ride requests, under different curb restrictions and SAV operational strategies. We focus on the following performance metrics: VKT, curb productivity, customer wait time, and customer...

Extreme Heat Disproportionately Increases Severe Road Traffic Crashes in High Conflict Settings and Among Vulnerable Road Users in California

Hsu, Cheng-Kai
Quistberg, D. Alex
Pérez-Ferrer, Carolina
Daniel Rodriguez
2026

Emerging evidence suggests that extreme heat elevates road-traffic injuries, undermining international road safety efforts like Vision Zero as global warming intensifies. However, the mechanisms underlying heat-related crashes remain poorly understood, with limited research linking heat exposure to specific crash types that may be driven by heat-induced unsafe road behaviors. Here, we analyzed temperature data and police-reported crash records—including detailed crash scene information—from 177 California cities (2012–2023) using a time-stratified case-crossover design, examining...

Navigating Uncertainty in Advanced Air Mobility: Scenario Planning for Policy Pathways at San Francisco International Airport

Susan Shaheen
Cohen, Adam
Wolfe, Brooke
2026

Advanced Air Mobility (AAM) includes innovative aviation technologies and services that could alter how people and goods are transported. However, future AAM growth and potential regional integration are uncertain and influenced by a range of factors. In this paper, we report findings from expert interviews (n = 35) and a scenario planning workshop (n = 32 stakeholders), conducted between August 2024 and July 2025, to explore potential alternative futures for AAM at the San Francisco International Airport (SFO) and the greater San Francisco Bay Area. We applied a two-axis framework:...

Plug-In Electric Vehicles in California: Review of Current Policies, Related Emissions Reductions for 2020, and Policy Outlook

Maggie Witt
Matthew Bomberg
Tim Lipman
Brett Williams
2012

California's emissions reduction goals for criteria air pollutants (CAPs) and greenhouse gases (GHGs) have encouraged policies that support plug-in electric vehicles (PEVs). This paper explores current and planned policies that promote PEVs, potential emissions benefits from PEV adoption in California by 2020, and future policy directions. The reviewed policies include the zero-emission vehicle regulations, the low-carbon fuel standard, and the clean car standards, which all require GHG reductions. Policies prompted by the California Public Utilities Commission Alternative-Fueled Vehicle...

Fuel Cell Systems: Total Cost of Ownership

Max Wei
Ahmad Mayyas
Tim Lipman
Hanna Breunig
Roberto Scataglini
Shuk Han Chan
Joshua Chien
David Gosselin
Nadir Saggiorato
Adam Weber
2019

Fuel cells are an electrochemical technology that are reaching the market in transportation and are a growing market in stationary power systems for backup power, primary power, combined heat and power, and materials handling equipment. The first part of this entry describes the manufacturing cost reductions from PEM and SOFC technologies that are estimated from higher-volume fuel cell manufacturing from economies of scale and improvements in overall yield. Fuel cells combined heat and power systems have the capability to displace grid electricity and on-site fuel combustion. In general...

A Total Cost of Ownership Model for Low Temperature PEM Fuel Cells in Combined Heat and Power and Backup Power Applications

Max Wei
Tim Lipman
Ahmad Mayyas
Joshua Chien
Shuk Han Chan
David Gosselin
Hanna Breunig
Michael Stadler
Thomas McKone
Paul Beattie
Patricia Chong
Whitney Colella
Brian James
2014

A total cost of ownership model is described for low temperature proton exchange membrane stationary fuel cell systems for combined heat and power (CHP) applications from 1-250kW and backup power applications from 1-50kW. System designs and functional specifications for these two applications were developed across the range of system power levels. Bottom-up cost estimates were made for balance of plant costs, and detailed direct cost estimates for key fuel cell stack components were derived using design-for-manufacturing-and-assembly techniques. The development of high throughput,...

Evaluating the Public Perception of a Feebate Policy in California Through the Estimation and Cross-Validation of an Ordinal Regression Model

Elliot Martin
Susan Shaheen
Tim Lipman
Madonna Camel
2014

Understanding the key factors influencing policy perception can be critical for informing the design of public policies. Feebates is a unique public policy that is meant to influence vehicle purchases. It presents buyers with a rebate for purchasing low-emission vehicles and a fee for purchasing high-emission vehicles. Because feebates directly impacts the consumer, understanding the dynamics of public perception, support, and opposition is important. This study explores the public perception of a potential feebate policy within California, and evaluates the robustness of an ordinal...

What Will Power the Hydrogen Economy? Present and Future Sources of Hydrogen Energy

Tim Lipman
2004

During the last ten to fifteen years advances in fuel cell technology have spurred an enormous wave of interest in hydrogen. This report first examines various methods for producing hydrogen, including discussion of the production potential for the United States. It then discusses and summarizes hydrogen distribution and delivery options, including a study of the environmental pollutant emissions implications and land and water use impacts of different production options. In addition, potential regional hydrogen production strategies around the U.S., and the potential for regional hydrogen...

Carbon Neutrality Study 1:Driving California’s Transportation Emissions to Zero

Austin Brown
Kelly Fleming
Tim Lipman
Lew Fulton
Jean Daniel Saphores
Gil Tal
Colin Murphy
Susan Shaheen
Bernadette Austin
Juan Carlos Garcia Sanchez
Elliot Martin
Marshall Miller
Michael Hyland
Susan Handy
Mark Delucchi
Daniel Coffee
J. R. DeShazo
2020

The purpose of this study overall is to explore the policy pathways to achieve a zero carbon transportation system in California by 2045. The purpose of this synthesis report is to describe the existing state of knowledge and policy related to energy use and greenhouse gas (GHG) emissions in the transportation sector, especially in California. It is an interim product of the larger study, which will use this report as the baseline and policy context sections. The report comprises four sections. Section 1 provides an overview of the major components of transportation systems and how those...

Safety and Capacity Analysis of Automated and Manual Highway Systems

Carbaugh, Jason
Godbole, Datta N.
Raja Sengupta
1999

This paper compares safety of automated and manual highway systems with respect to result- ing rear-end collision frequency and severity. The results show that automated driving is safer than the most alert manual drivers, at similar speeds and capacities. We also present a detailed safety-capacity tradeo study for four di erent Automated Highway System concepts that di er in their information structure and separation policy.