Sustainability

Projected Changes in Heatwaves Over Central and South America Using High-Resolution Regional Climate Simulations

Ramarao, MVS
Arunachalam, S
Sánchez, BN
Schinasi, LH
Rodriguez, D
Dronova, I
O'Neill, MS
Avila-Palencia, I
Gouveia, N
Ju, Y
Kephart, J
2024

Heatwaves (HWs) pose a severe threat to human and ecological systems. Here we assess the projected changes in heatwaves over Latin America using bias corrected high-resolution regional climate simulations under two Representative Concentration Pathway scenarios (RCPs). Heatwaves are projected to be more frequent, long-lasting, and intense in the mid-century under both RCP2.6 and RCP8.5 scenarios, with severe increases under the RCP8.5 scenario. Even under the low emissions scenario of RCP2.6, the frequency of heatwaves doubles over most of the region. A three- to tenfold rise in population...

Alternative Traffic Signal Illumination

Cohn, Theodore E.
Greenhouse, Daniel
Knowles, Richard
1998

New technologies have enabled the production of traffic signals that have significant advantages over standard incandescent signals, including greater energy efficiency and lower maintenance costs. Before the new signals are installed in the field, it is important to assure that they as visible as the older signals. We have developed a quality index we term the usability factor (UF) which can be used to evaluate the visibility of a new device relative to that of a standard reference lamp. We have measured UF's of a variety of new types of lamps by means of heterochromatic flicker...

Health and Environmental Co-Benefits of City Urban Form in Latin America: An Ecological Study

Avila-Palencia, I
Sánchez, BN
Rodríguez
Perez-Ferrer
Miranda, J
Gouveia, N
Bilal, U
Useche, A
Wilches-Mogollon, M
Moore, K
Sarmiento, O
Roux, AV Diez
2022
We investigated the association of urban landscape profiles with health and environmental outcomes, and whether those profiles are linked to environmental and health co-benefits. In this ecological study, we used data from 208 cities in 8 Latin American countries of the SALud URBana en América Latina (SALURBAL) project. Four urban landscape profiles were defined with metrics for the fragmentation, isolation, and shape of patches (contiguous area of urban development). Four environmental measures (lack of greenness, PM2.5, NO2, and carbon footprint), two...

The Dynamics of the California Electric Grid Mix and Electric Vehicle Emission Factors

Zhang, Xingrui
Martin, Elliot
Shaheen, Susan
2025

Electric vehicle (EV) emissions occur when a vehicle is charged and are based on the mix of power sources used during that period. The rapid growth of solar and wind energy has introduced a high degree of variability in the emissions of the grid for both diurnal and annual periodicities. Growth in solar energy has been particularly prominent in California. Using grid mix data spanning April 2018 to April 2023 from the California Independent System Operator (CAISO) and power source emission factors, we evaluate the grid mix at 5 min intervals and estimate the emission factors based on the...

Environmental Impacts of Transportation Network Company (TNC)/Ride-Hailing Services: Evaluating Net Vehicle Miles Traveled and Greenhouse Gas Emission Impacts within San Francisco, Los Angeles, and Washington, D.C. Using Survey and Activity Data

Martin, Elliot
Shaheen, Susan
Wolfe, Brooke
2024

Transportation Network Companies (TNCs) play a prominent role in mobility within cities across the globe. However, their activity has impacts on vehicle miles traveled (VMT) and greenhouse gas (GHG) emissions. This study quantifies the change in personal vehicle ownership and total miles driven by TNC drivers in three metropolitan areas: San Francisco, CA; Los Angeles, CA; and Washington, D.C. The data sources for this analysis comprise two surveys, one for TNC passengers (N = 8630) and one for TNC drivers (N = 5034), in addition to data provided by the TNC operators Uber and Lyft. The...

Can Electric Vehicle Carsharing Bridge the Green Divide? A Study of BlueLA’s Environmental Impacts among Underserved Communities and the Broader Population

Yassine, Ziad
Martin, Elliot W.
Shaheen, Susan A.
2024

This study aims to evaluate the potential of electric vehicle (EV) carsharing services to address social and environmental disparities in urban transportation through an evaluation of BlueLA, a one-way station-based carsharing service in Los Angeles, California. BlueLA provides a clean and affordable mobility option in underserved communities that face significant air quality burdens and have historically been excluded from environmental benefits. By incorporating BlueLA trip activity data from January 2021 to December 2022 (n = 59,112 trips) and an online user survey implemented in early...

More Needs to Be Done to Lower Costs for Ridehailing Drivers to Shift to Electric Vehicles

Shaheen, Susan
Martin, Elliot
Ju, Mengying
2025

Transportation network companies (TNCs) have played an increasingly prominent role providing on-demand mobility for consumers across California. The California Public Utilities Commission (CPUC) and the California Air Resources Board (CARB) have adopted and are implementing SB 1014 (Clean Miles Standard), which establishes an annual increase in the percent of zero-emission passenger miles traveled and greenhouse (GHG) emission reduction targets for TNCs. This regulation requires TNC drivers to acquire and operate an electric vehicle (EV).

PATH ITS Research Digests

Chira-Chavala, Ted
2001

Ramp meters are commonly used to relieve congestion on freeways. What is the value of these systems? Ramp metering can alleviate recurrent, regular traffic congestion, such as that caused by the daily commute. The goal is usually to maintain uninterrupted freeway flow at a certain acceptable level, but it transfers delay to the entrance ramp, where excess demand is forced to wait. This report summarizes ramp metering technologies, reviews the algorithms commonly used with them, and uses a traffic simulation model to identify the benefits and costs of using these systems. We used a...

Steady State Conditions on Automated Highways

del Castillo, Jose M.
Lovell, David J.
Daganzo, Carlos F.
1995

This paper is concerned with technical investigations of traffic operations on automated highways. Estimates are made of the steady-state capacity of such freeways, paying particular attention to the effect of entry and exit maneuvers. The possibility of scheduling departing vehicles appropriately into platoons to minimize extraneous maneuvers is investigated. Characteristics of urban areas likely to be candidates for automated freeways are discussed, and some shortcomings of automated freeways, vis-à-vis conventional freeways, are pointed out. Finally, some areas of future research needs...

Identification and Prioritization of Environmentally Beneficial Intelligent Transportation Technologies: Modeling Effort

Young, Troy
Sperling, Daniel;
Shaheen, Susan
1999

In 1996, California Partners in Advanced Transit and Highways (PATH) commissioned a project team led by the Institute of Transportation Studies, University of California at Davis with the Claremont Graduate School to undertake a review of the environmental impacts of Intelligent Transportation Systems (ITS). The objectives of this project were to: 1) review previous qualitative and quantitative environmental assessments of ITS, from both field operational tests and modeling studies; 2) review the regulatory and policy contexts which encompass ITS; 3) develop a modeling framework suitable...