published journal article

Traffic Trumps All: Examining the Effect of Traffic Impact Analyses on Urban Housing

Abstract

Traffic impact analysis (TIA), which estimates the nearby traffic effects of proposed land development, tends to bias against higher-density developments in urban areas where traffic is often heavy and travel alternatives plentiful. This has important implications for housing supply and affordability, suburban sprawl, and private vehicle dependence. We examine the understudied implications of TIA on housing by drawing on empirical evidence from distinct bodies of research in the transportation and land use planning literature to describe the mechanisms through which TIA may affect housing markets. We conclude that TIAs likely have negative effects on both urban housing production and affordability.

policy brief

Traffic Trumps All: Examining the Effect of Traffic Impact Analyses on Urban Housing

Abstract

Traffic impact analyses (TIA) are widely used by local governments to assess the traffic impacts of proposed land use developments. TIAs are often measured in terms of expected changes to traffic flows through nearby intersections using a metric called “level of service” (LOS). This process tends to be biased against higher-density developments in urban areas where traffic is already congested and travel alternatives are plentiful. Researchers have found that the projected traffic impacts of developments in already built-up areas tend to be overestimated, which leads to higher traffic impact fees and related costs associated with the TIA process. Often, local residents use such analyses as evidence to oppose new developments on traffic grounds. The result is that TIAs can help discourage new housing production in built-up areas where demand is greatest, which likely exacerbates the housing affordability crises in places like California.In essence, the logic of TIAs is that the human activities and the built environment in cities should vary to keep nearby traffic flowing smoothly. The fundamental problem with LOS-based TIAs is that they measure vehicle mobility and not the more fundamental goals of economic and social accessibility. While California has been a national leader in changing the metric by which traffic impacts are evaluated under the California Environmental Quality Act, from LOS to vehicle miles of travel effects, LOS-based analyses of development proposals are still typically conducted by local governments — even in the Golden State.This study reviewed and synthesized research on TIAs and their effects on land use planning, and found that mobility-focused transportation planning likely contributes to the housing affordability crisis plaguing many places. Further, research shows that gradually shifting away from mobility-centered metrics, like LOS, and toward more accessibility-centered evaluation tools, will enable more comprehensive assessments of development impacts, which could help ease California’s housing affordability crisis.

policy brief

Environmental Reviews Fail to Accurately Analyze Induced Vehicle Travel from Highway Expansion Projects

Publication Date

January 1, 2021

Author(s)

Abstract

Induced travel is a well-documented effect in which expanding highway capacity increases the average travel speed on the highway, which in turn reduces the perceived “cost” of driving and thereby induces more driving. This increase in vehicle miles traveled (VMT) increases congestion (often back to pre-expansion levels) and air pollutant emissions, reducing or eliminating the purported benefits of the expansion. Yet highway expansion projects continue to be proposed across California, often using congestion relief—and sometimes greenhouse gas reductions—as a justification for adding lanes. These rosy projections about the benefits of highway expansion projects indicate that the induced travel effect is often not fully accounted for in travel demand models or in the projects’ environmental review process.With this problem in mind, researchers at the University of California, Davis developed an online tool to help agencies estimate the VMT induced annually by adding lanes to major roadways in California’s urbanized counties. The researchers also applied the calculator to estimate the vehicle travel induced by five highway expansion projects in California that had gone through environmental review within the past 12 years. They then compared their estimates with the induced travel analysis completed for the projects’ actual environmental impact assessments. This policy brief summarizes findings from that research, along with policy implications.View the NCST Project Webpage

Assessing the Potential for Densification and Reduction of Vehicle Miles Traveled in Areas Without Rail

Status

Complete

Project Timeline

June 21, 2022 - October 31, 2023

Principal Investigator

Project Summary

While transportation infrastructure and efficiency should inform where to build more housing, little is known about how housing allocation and development processes can be coordinated more systematically with transportation. To date, transportation-housing coordination has often relied on the densification of areas near rail transit stations, putting heavy
burdens on these locations and their residents. Much less attention has been paid to how densification can be achieved in a more equitable manner by encompassing other sites.

This research seeks to better understand equity issues and other challenges that may arise in pursuing transportation-informed densification. The research includes two components: 1) a scenario analysis of the potential impacts of SB 743 that highlights equity concerns, as well as difficulties in identifying low vehicle miles traveled locations, and 2) a qualitative, in-depth investigation, including interviews with policy experts, creators, implementers, and advocates that explore ways to achieve more inclusive densification of non-rail transit areas, which have long been neglected in the literature. Overall, the findings suggest that transportation-informed densification is a challenging process, and this is particularly true when it comes to implementation and inclusive place-making. More needs to be known about how densification can take place in a way that promotes diversity, equity, and inclusion rather than causing disproportionate impacts on disadvantaged communities and their residents.

other

Press Release: Not Going Out is the “New Normal” Post-Covid, Say Experts

research report

Is Micromobility Being Used in Place of Car Trips in Daily Travel (or “Trip Chains”)?

Abstract

To understand the extent to which micromobility services such as bike-share and scooter-share are enabling car-lightlifestyles by replacing driving, this report explores the trip-chaining patterns of micromobility users. The research team used travel diary data collected from micromobility users in 48 cities across the US. Findings from their analysis shows that a considerable portion of car owners are leaving their cars at home when using micromobility. This suggests that, for a subset of users, micromobility can form part of a car-free or car-light day of travel, despite having a car available. In addition, micromobility services are supportive of complex trip chains that include both work and non-work trips with reduced reliance on cars. The use of micromobility services tends to entirely replace shorter car trips on shorter-length trip chains.

Our Experts

Nicholas Marantz

Associate Professor, Department of Urban Planning and Public Policy, UC Irvine

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Research Team:

Jae Hong Kim (lead), Jesus M. Barajas, Douglas Houston, Nicholas Marantz

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UC Davis, UC Irvine

Research Team:

Jamey Volker (lead), Susan Pike, Nicholas Marantz

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UC Davis, UC Irvine

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Research Team:

Michael Zhang (lead), Egon Terplan, Qiao Yu, Jiaqi Ma, Mollie Cohen D'Agostino, David Brownstone, Craig Rindt, Brain He, Yifang Zhu, Michael Manville, Jean-Daniel Saphores

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UC Davis, UC Irvine, UCLA

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Michael Manville (lead), Hao Ding

UC Campus(es):

UCLA

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Pei (Peggy) Wang (lead), Rui Lin

UC Campus(es):

UC Berkeley

Research Team:

Pei (Peggy) Wang (lead), Rui Lin

UC Campus(es):

UC Berkeley

Research Team:

Pei (Peggy) Wang (lead), Ching-Yao Chan

UC Campus(es):

UC Berkeley

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Research Team:

Jane Macfarlane (lead), Joan Walker

UC Campus(es):

UC Berkeley

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Joan Walker (lead), Johanna Zmud, Phoebe Ho

UC Campus(es):

UC Berkeley

Research Team:

Susan Shaheen (lead), Adam Cohen, Madeline Brozen, Evelyn Blumenberg, Joan Walker, Rasik Hussain, Nicole Matteson, Aqshems Nichols

UC Campus(es):

UC Berkeley, UCLA