Policy and Literature Review on the Effect Millennials Have on Vehicle Miles Traveled, Greenhouse Gas Emissions, and the Built Environment

Status

Complete

Project Timeline

Principal Investigator

Project Team

Michelle E. Zuniga

Campus(es)

UC Irvine

Linking Statewide and Regional Travel Models to Estimate Interregional Travel Impacts in California

Status

In Progress

Project Timeline

October 1, 2016 - June 30, 2024

Principal Investigator

Campus(es)

UC Irvine

Project Summary

Metropolitan Planning Organizations (MPOs) use regional travel forecasting models to estimate vehicle trips (VT), average speeds, and vehicle miles traveled (VMT), which serve in turn as input to regional emission models. Interregional travel is not usually part of MPO models, but it is explicitly part of statewide models. The California Statewide Travel Demand Model (CSTDM) is an activity-based model that produces statewide origin-destination trip tables for assignment to the statewide network. Consistency tests, however, suggest that there are significant deviations between link counts from the CSTDM and those from regional models, as measured at defined cordon stations. These trip counts are, by definition, interregional travel – travel that is typically generated within a region but with performance impacts in another region or in areas not formally part of a defined region.

The proposed project seeks to develop and test methods to synchronize the travel forecasting results of the CSTDM with regional travel forecasting models, with the objective of better estimating interregional travel and greenhouse gas emissions in California. Whether trip-, tour-, or activity-based, CSTDM and all current regional models apply conventional trip assignment as the last step in the modeling process. From the perspective of potential policies to address performance impacts, this study will resolve how regions and the state properly account for the relative proportion of interregional travel and the associated travel impacts. The methodological problem is to synchronize the assigned and validated cordon counts produced by regional models with those generated as part of assignment in the CSTDM. Techniques to modify origin-destination trip tables exist but applications above the local area have been rare. The CSTDM trip tables will be updated to reflect the assigned counts at defined MPO cordon stations. At least two methods will be tested using Caltrans’ Performance Measurement System (PeMS) data with CSTDM trip tables and using MPO cordon estimates with CSTDM trips tables. Each method will be evaluated, with one selected for final application based on its consistency across all model levels and data sources.

Do Compact, Accessible, and Walkable Communities Promote Gender Equality?

Status

Complete

Project Timeline

Principal Investigator

Clean Air in Cities: Impact of the Layout of Buildings in Urban Areas on Pedestrian Exposure to Ultrafine Particles from Traffic

Status

Complete

Project Timeline

Principal Investigator

Project Team

Liye Zhu, Dilhara Ranasinghe, Marcelo Chamecki, Michael J. Brown

Project Summary

Southern California is no stranger to auto-related pollution. Areas near roadways typically demonstrate much higher pollutant concentrations; as a result, pedestrians and residents in these areas face greater exposure to air pollutants. In dense urban areas like Los Angeles, near-roadway environments can include most street-level outdoor spaces. At the same time, traffic-related pollution levels in urban areas are highly variable. Although the connection between built environment and street-level pollutant concentrations is a nascent field of study, it is clear that the design of the built environment plays a major role on pollution concentration.

The researchers examined the effects of different built environment designs on the concentrations of street-level ultrafine particles (UFP) at the scale of several blocks using the Quick Urban and Industrial Complex (QUIC) numerical modeling system. They evaluated the effects of several built environment designs, changing building heights and spacing while holding total built environment volumes constant. They found that ground-level open space reduces street-level pollutant concentrations. Holding volume/surface area constant, tall buildings clustered together with larger open spaces between buildings resulted in substantially lower pollutant concentrations than buildings in rows. Buildings arranged on a ‘checkerboard’ grid with smaller contiguous open spaces, a configuration with some open space on one of the sides of the roadway at all locations, resulted in the lowest average concentrations for almost all wind directions. Rows usually prohibit mixing for perpendicular and oblique wind directions, even when there are large spaces between them, and clustered buildings have some areas where buildings border both sides of the roadways, inhibiting mixing. The model results suggest that pollutant concentrations drop off rapidly with height in the first 10 m or so above the roadways. In addition, the simulated vertical concentration profiles show a moderate elevated peak at the roof levels of the shorter buildings within the area. Model limitations and suggestions both for urban design are both discussed.

Transit Investment Impacts on Land Use Beyond the Half-Mile Mark

Status

Complete

Project Timeline

Principal Investigator

Project Team

Ashley (Wan-Tzu) Lo, Jaewoo Cho

policy brief

An L.A. Story: The Impact of Housing Costs on Commuting

Abstract

Concerns about the environmental impacts of transportation have made reducing vehicle miles traveled (VMT) a policy priority. One way to decrease VMT is to decrease the length of commuting trips, and to get commuters out of their private vehicles. Although many studies have investigated the determinants of commuting, few have analyzed the linkage between housing costs and commuting.

To address this gap, researchers at UC Irvine developed a model that jointly explains commuting time and distance, and accounts for residential self-selection (i.e., where someone chooses to live), the effect of car ownership, and key land use characteristics around both residences and workplaces. The research focused on Los Angeles County. Census data shows that the average commute time for Los Angeles County residents pre-pandemic was 32.8 minutes, 18.8 percent higher than the national average.

policy brief

Grocery Shopping in California and COVID-19: Transportation, Environmental Justice, and Policy Implications

Abstract

The COVID-19 pandemic upended many aspects of our lives, including how we shop for groceries. As grocery stores scaled back their opening hours and managed access, many shoppers switched to online shopping with home delivery (“e-grocery”) or store pick-up (“click-and-pick”). Few empirical studies published to date have explored how the COVID-19 pandemic changed grocery shopping, the extent to which these changes may last, how the pandemic exacerbated grocery store access inequalities, and how access to groceries in California is intertwined with environmental justice concerns. Moreover, most studies on this topic were based on non-random samples, which can provide quick results in a fast-changing environment but their findings are not generalizable.

This brief explores the effects of changing grocery shopping trends on disadvantaged communities in California. Using data obtained by surveying California members of KnowledgePanel,® the largest and oldest online probability-based panel representative of the U.S. population, the research team explored the frequency of grocery shopping in California and likelihood of it changing after the pandemic; the types of stores Californians shopped in for groceries during the pandemic and who used grocery delivery companies; and how / if environmental justice factors played a role in observed changes in grocery shopping.

published journal article

Peaked Too Soon?: Analyzing the Shifting Patterns of P.M. Peak Period Travel in Southern California

Abstract

Daily vehicle travel collapsed with the onset of the COVID-19 pandemic in early 2020 but largely bounced back by late 2021. The pandemic caused dramatic changes to working, schooling, shopping, and leisure activities, and to the travel associated with them. Several of these changes have, so far, proven enduring. So, while overall vehicle travel had largely returned to pre-pandemic levels by late 2021, the underlying drivers of this travel have likely changed.

This research examines one element of this issue by analyzing whether patterns of daily trip-making shifted temporally between the fall of 2019 and 2021 in the Greater Los Angeles megaregion. The research team used location-based service data to examine vehicle trip originations for each hour of the day at the U.S. census block group level in October 2019 and October 2021. The team observed notable shifts in the timing of post-pandemic PM peak travel, so the researchers examined changes in the ratio of mid-week trips originating in the early afternoon (12–3:59 PM) and the late afternoon/early evening (4–7:59 PM).

The research paper includes a clear shift in the temporal distribution of PM trip-making, with relatively more late PM peak period trip-making prior to the pandemic, and more early PM peak trip-making in 2021. The peak afternoon/evening trip-making hour shifted from 5–5:59 PM to 3–3:59 PM. The researchers also found that afternoon/evening trip-making each year is largely explained by three workplace-area/school-area factors: (1) the number of schoolchildren in a block group (earlier); (2) block groups with large shares of potential remote workers (earlier), and (3) block groups with large shares of low-wage jobs and workers of color (later, except for Black workers in 2021). The team found the earlier shift in PM peak travel between pre- and late-pandemic periods to be explained most by (1) higher shares of potential remote workers and (2) higher shares of low-wage jobs and workers of color. These findings suggest that the rise of working from home has likely led to a shift in PM peak travel earlier in the afternoon when school chauffeuring trips are most common. This is especially true for low-income workers and workers of color.

policy brief

Did COVID-19 Fundamentally Reshape Telecommuting in California?

Abstract

Health concerns and government restrictions during the COVID-19 pandemic caused a sharp increase in telecommuting (i.e., doing paid work at home or possibly an alternate worksite). In addition to reducing vehicle miles traveled (VMT), decreasing energy use, and lowering emissions of air pollutants and greenhouse gases (GHG), telecommuting may offer numerous other co-benefits, including increasing the worker pool, decreasing time and costs associated with travel, improving work-life balance, and decreasing stress. It may also stimulate greater use of non-motorized and active modes of travel (e.g., walking, biking, taking transit). However, telecommuting (especially during the pandemic) may also affect remote workers’ opportunities for promotion and ties with colleagues, health, work-life balance for families with children (childcare and schools did not operate normally during the pandemic), and even work productivity. It may also increase commuting length because telecommuters tend to live in more suburban areas, usually associated with fewer transit options and a higher likelihood of car use. While a large body of literature on telecommuting existed before COVID-191, this research looked at how the frequency of telecommuting changed in California during the pandemic, and how it may evolve. Whereas most previous research relied on non-random samples, the dataset used for this research was collected at the end of May 2021 by Ipsos, which randomly sampled Californian members of KnowledgePanel©, is the largest probability-based online panel in the nation, so the results are generalizable to California’s population. Quantifying changes in telecommuting is important for updating sustainable community strategies created by Metropolitan Transportation Organizations and gauging telecommuting’s likely contribution to meeting California’s GHG reduction targets. Moreover, analyzing telecommuting frequency for different socio-economic groups and occupations should help policymakers understand the long-term impacts of the pandemic on different segments of the labor market.