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This paper explores the enduring impact of freeway construction on urban neighborhoods and communities, focusing on Los Angeles. The legacy of freeways in Los Angeles, often and purposefully constructed through marginalized communities during the mid-20th century for the benefit of white suburbanites, is reflected in significant social, economic, and environmental symptoms today. This paper also examines de-freeway methods to reconnect these divided communities, assessing their need and effectiveness through data analysis and case studies.The case studies presented in this paper offer a diverse range of solutions. They include the capping of I-5 for Freeway Park in Seattle, the tunneling of the Central Artery for Boston's Big Dig, the activation of I-5 underpasses for Chicano Park in San Diego, and the creation of the Ricardo Lara embankment park along the I-105 freeway in Lynnwood. These examples provide valuable insights into the processes, challenges, and successes of de-freeway and community reconnection efforts, showcasing the adaptability of these solutions in different urban contexts.The paper introduces three design proposals for freeway sites across six communities in Los Angeles. These proposals are guided by urban reformation around freeways and incorporating urban design principles prioritizing social equity, environmental sustainability, and economic revitalization for the most vulnerable and impacted communities. The proposed designs aim to restore community cohesion and foster resilient urban ecosystems.This study contributes to the ongoing discourse on sustainable urban transformation and the reclamation of public spaces for community benefit by providing a comprehensive analysis of historical impacts and contemporary solutions. The paper's findings should help inform and guide urban planning and policy advocates and professionals inspired by the reconnecting communities movement, underscoring the need for innovative approaches to mending bifurcated and ecologically disadvantaged communities.

We examine the barrier effects of freeways in California. We analyze the association between freeways and nearby street network connectivity and quantify the frequency and quality of crossings—underpasses or bridges that enable pedestrians and cyclists to cross the freeway. We find that barrier effects are most pronounced in communities of color. We also find that even where crossings exist, they are unpleasant or even hazardous for pedestrians and cyclists because of high-speed traffic on on- and off-ramps, and because large volumes of traffic are funneled through a small number of crossings rather than being distributed over a wider network.

Freeway and arterial transportation networks in most districts are managed separately without any coordination. This lack of coordination increases the severity of traffic congestion when one or both systems reach their capacities. Some field studies have observed reductions in travel time by coordinating freeway ramps with adjacent arterial signals. To advance the investigation, we propose an integrated traffic management strategy that involves variable speed limit, lane change, ramp metering for freeway traffic flow control, and a traffic-responsive signal control scheme for adjacent traffic light intersections.The variable speed limit and lane change control are designed to alleviate congestion at a lane-drop bottleneck in an arbitrary section, and reject potential uncertainties from measurements or model parameters. The ramp metering algorithm takes advantage of the signal plan of neighboring arterial intersection when estimating on-ramp demands. The signal plan for each arterial intersection is determined by a simulation-based cycle length model and estimated demands of all directions, part ofwhich depend on off-ramp flow measurements. The above data sharing mechanism strengthens the connection between thefreeway and arterial networks and enhances the control performance. We demonstrate the effectiveness and quantify the benefits provided by the proposed system in terms of traffic mobility, safety and emission using microscopic traffic simulations.View the NCST Project Webpage

The COVID-19 pandemic, characterized by travel restrictions and reduced traffic volumes, heightened the risk of severe single-vehicle crashes on Florida's freeways. This study utilized random parameter multinomial logit models, accounting for heterogeneity in means and variances, to analyze driver injury severities in 2020 and compare variations in the magnitude of factors contributed to these injuries across different freeway systems. The estimated models identified 31 statistically significant variables across Florida's major freeways (I-4, I-10, I-75, and I-95). Among these variables, only two—normal driving and restraint usage—were statistically significant across all four freeway systems. Moreover, the model results indicated that factors contributing to severe driver injuries were most prominent on I-95 compared to the other freeways in 2020. These findings improve our understanding of freeway safety measures during a pandemic and provide valuable insights to enhance traffic management strategies for state highway agencies, prioritizing operational safety in potential future pandemics. [ABSTRACT FROM AUTHOR]

This project uses mixed methods to examine the systemic causes and consequences of the construction of Stockton, California’s Crosstown Freeway and of urban redevelopment for Asian Americans communities. Stockton underwent spatial restructuring in the decades after the Second World War, and state and local government contributed and responded to these changes by implementing connected freeway and urban renewal programs. Historical and contemporaneous xenophobia and racism placed Chinatown, Japantown, and Little Manila in their path, with these enclaves deemed blighted and subject to “slum clearance.” The choice of freeway route was racially biased. The neighborhood surrounding an unchosen route was predominantly white, whereas that of the chosen route was predominantly home to people of color. Freeway construction during the 1960s and 1970s directly displaced hundreds of people and housing units downtown— mainly people of color, particularly Asians. The communities most harmed were the Asian American enclaves, where the housing stock declined by about three quarters between 1960 and 1970. The losses were not only physical, as the freeway and redevelopment eviscerated once vibrant ethnic commercial hubs. Because of long-standing economic and political marginalization, Asian Americans were relatively powerless to prevent the destruction; nonetheless, they fought to build affordable housing for their people, protect and in some cases relocate cultural institutions, and support surviving ethnic businesses. In the long run, Stockton failed to revitalize its downtown, while destroying its cultural diversity. The findings can help reform and improve professional practice within the transportation arena to ensure racial fairness and equity.

In recent decades, homelessness has become an increasingly major challenge in the U.S., reaching about half million unhoused people. Many of them seek shelter in settings such as freeways, underpasses, and rest areas. State departments of transportation (DOTs) are responsible for the health and safety of these settings and their occupants, housed and unhoused. This study synthesizes existing literature and findings from interviews with staff from 13 state DOTs and eight service providers and organizations responding to homelessness. Homelessness represents a recognized and common challenge for DOTs, which face jurisdictional, financial, and legal hurdles in addressing it. DOT staff employ both “push” and “pull” strategies, the most common of which is encampment removals (“sweeps”). However, the effectiveness of such removals is limited, as encampments often reappear in nearby sites. Other strategies include “defensive design” and, more proactively, establishing or partnering with low-barrier shelters, providing shelters and sanitation on DOT land, and coordinating rehousing and outreach efforts. Our findings suggest that DOTs should acquire better data on homelessness on their lands, create a homelessness coordinating office, establish formal partnerships with nonprofits/service providers, and evaluate the necessity of encampment removals, through the development and utilization of prioritization criteria.

In recent decades, homelessness has become an increasingly major challenge in the U.S. Of the half million unhoused people in the U.S., many seek shelter in settings under the auspices of state departments of transportation (DOTs), such as freeways, underpasses, and rest areas. DOTs are responsible for the health and safety of these settings and of their occupants, housed and unhoused.This study synthesizes existing literature and findings from interviews with staff from 13 state DOTs and eight service providers and organizations responding to homelessness. Homelessness represents a recognized and common challenge for DOTs, but the numbers and location of unhoused individuals in state transportation settings vary and fluctuate. As DOTs face jurisdictional, financial, and legal hurdles in responding, DOT staff employ both “push” and “pull” strategies, the most common of which is encampment removals. However, the effectiveness of such removals is limited. Other strategies include “defensive design” and, more proactively, establishing or partnering with low-barrier shelters, providing shelters and sanitation on DOT land, and coordinating rehousing and outreach efforts. Our findings suggest that DOTs should acquire better data on homelessness on their lands, create a homelessness coordinating office, establish formal partnerships with nonprofits/service providers, and evaluate the necessity of encampment removals, through the development and utilization of prioritization criteria. DOTs should coordinate with other bodies as they work towards broader housing solutions.

Vehicular air pollution has created an ongoing air quality and public health crisis. Despite growing knowledge of racial injustice in exposure levels, less is known about the relationship between the production of and exposure to such pollution. This study assesses pollution burden by testing whether local populations' vehicular air pollution exposure is proportional to how much they drive. Through a Los Angeles, California case study we examine how this relates to race, ethnicity, and socioeconomic status---and how these relationships vary across the region. We find that, all else equal, tracts whose residents drive less are exposed to more air pollution, as are tracts with a less-White population. Commuters from majority-White tracts disproportionately drive through non-White tracts, compared to the inverse. Decades of racially-motivated freeway infrastructure planning and residential segregation shape today's disparities in who produces vehicular air pollution and who is exposed to it, but opportunities exist for urban planning and transport policy to mitigate this injustice.

We examine the barrier effects of freeways in California. We analyze the association between freeways and three measures of nearby street connectivity: the composite Street Network Disconnectedness index (SNDi), circuity, and the distance between crossings – underpasses or bridges that enable people to cross the freeway. We also assess the quality of a sample of these crossings for pedestrians and cyclists. We find that barrier effects are most pronounced in communities of color. We also find that even where crossings exist, they are unpleasant or even hazardous for pedestrians and cyclists because of high-speed traffic on on- and off-ramps, and because large volumes of traffic are funneled through a small number of crossings rather than being distributed over a wider network.