Archives: Research Products

By Transit, By-Right: How Housing Development Approval Processes Can Support Higher Transit-Friendly Density

Abstract

Connected and automated vehicle (CAV) technologies attracted extensive attention in the past decade. As CAV brings convenience to travel, people’s travel behaviors and patterns might change significantly. Existing models, however, cannot comprehensively evaluate the impacts on transportation systems. This study adopted an activity-based approach to evaluate the comprehensive CAV impacts on the transportation system in Southern California. A stated preference survey was conducted and captured people’s behavior changes associated with CAV deployment. The model prediction demonstrated that the total trip number increased by 9%, with a 13% growth in total car-like mode travel distance. Among all trip purposes, work trips contributed to 49% of total trip number growth and 75% of the increased car-like mode travel distance. The advanced CAV technology alone wouldn’t directly benefit future transportation systems and it is still critical to have appropriate policy interventions in place.

Related Publications

published journal article

Connected automated vehicle impacts in Southern California part-II: VMT, emissions, and equity

policy brief

Connected and Automated Vehicle Impacts in Southern California: Travel Behavior, Demand, and Transportation System Perspectives

presentation

Activity-Based Travel Behavior and Demand Analysis in the Era of CAV

published journal article

Does Discretion Delay Development?

Publication Date

November 15, 2022

Associated Project

Author(s)

Shane Phillips, Nolan Gray, Michael Manville, Paavo Monkkonen

Areas of Expertise

Analyzing the strengths and weaknesses of the 85th percentile rule

Abstract

Problem, research strategy, and findings:
Local governments sometimes approve multifamily housing through a discretionary process, meaning a public body must vote to entitle the proposal before it can seek a building permit. By-right entitlement, in contrast, allows developers to apply directly for a building permit. We tested the hypothesis that by-right approvals are faster. Faster approval can make multifamily development more feasible, which can in turn improve housing affordability. Analyses of approval pathways are often confounded by project size and complexity, but we exploited a provision in the Los Angeles Transit-Oriented Communities (TOC) program that allowed many large projects to use by-right approval. Using data from roughly 350 multifamily projects permitted in Los Angeles (CA) from January 2018 through March 2020, we compared approval timelines for both by-right and discretionary projects. We found that by-right projects were permitted 28% faster than discretionary projects, controlling for project and neighborhood characteristics. By-right projects also had less variance in their approval times, suggesting that by-right approval offers not just more speed but more certainty.

Takeaway for practice:
Planners should create more opportunities for multifamily housing to be permitted by right. Despite some selection bias in our study, evidence from the TOC program suggests that creating a by-right option would accelerate approval time and thus substantially benefit housing production. The faster approval timelines, moreover, have been accompanied by an increase in average project size and the number of units reserved for low-income households.

Related Publications

policy brief

By Transit, By-Right: Impacts of Housing Development Approval Processes on Transit-Supportive Density

published journal article

The Eighty-Five Percent Solution: A Historical Look at Crowdsourcing Speed Limits and the Question of Safety

Publication Date

June 30, 2020

Associated Project

Areas of Expertise

Safety, Public Health, & Mobility Justice

Safety, Public Health, & Mobility Justice

Abstract

The “85th percentile rule” is commonly used to set speed limits in jurisdictions across the U.S. Modern interpretations of the rule are that it satisfies key conditions needed for safe roadways: it sets speed limits deemed reasonable to the typical, prudent driver, reduces the problematic variance in travel speeds among vehicles, and allows law enforcement to focus on speeding outliers. Authoritative publications regularly assert that the rule came about because early driving surveys often found that drivers moving at or below the 85th percentile of a speed on a given roadway were within one standard deviation of the mean speed for that roadway and were in the low involvement group for traffic incidents. But does this widely used rule for setting speed limits really have such a scientific pedigree? Given debates in cities around the U.S. about competing uses of street space, we examine where this rule of driver-set speed limits actually came from and whether rule developers’ rationales still hold true today. While most observers trace the rule to safety research and a 1964 report, we find that the 85th percentile rule actually emerged decades earlier amidst the nascent traffic engineering profession’s preoccupation with “traffic service” to increase vehicular throughput; and with respect to safety, the rule was explicitly intended as a starting point in speed limit setting, and not the last word.

policy brief

The Eighty-Five Percent Solution: Is Crowdsourcing Speed Limits the Best Approach to Traffic Safety?

Publication Date

September 1, 2020

Author(s)

Brian D. Taylor, Mark Garrett, Yu Hong Hwang

Areas of Expertise

From Traffic Impact Analysis to Accessibility Impact Analysis: Developing and Testing a Next Generation Development Impact Analysis Tool

Abstract

Setting appropriate speeds on roadways requires balancing the economic and social benefits of higher vehicle speeds on one hand, against the greater safety, environmental, and human activity costs of fast-moving traffic on the other. While drivers and commercial shippers typically favor faster limits, those living, walking, biking, or playing in proximity to roads often want slower limits. The most common method for setting speed limits, however, leaves it to drivers to collectively decide how fast is too fast. According to the U.S. Federal Highway Administration (FHWA), most places in North America set speed limits using the “85th-percentile rule.” This long-established standard calls for observing the speeds of free-flowing traffic on a roadway without posted speed limits, and then setting the limit at a 5 mph increment above or below the speed at which 85% of vehicles travel. So, for example, if 85% of drivers on a particular road are observed to travel at 43 mph or less, the speed limit would be set at 45 mph.

other

Working Paper: How Does Traffic, or the Fear of it, Affect Housing Affordability? Examining the Effect of Traffic Impact Analysis on Housing Production and Affordability

Publication Date

May 1, 2021

Associated Project

Author(s)

Hao Ding, Brian D. Taylor

Areas of Expertise

From Traffic Impact Analysis to Accessibility Impact Analysis: Developing and Testing a Next Generation Development Impact Analysis Tool

View other

Abstract

Traffic impact analysis (TIA), which estimates the traffic impacts of proposed land development, tends to bias against higher-density developments in urban areas where traffic is often congested and travel alternatives plentiful. This has important implications for housing supply and affordability, suburban sprawl, and private vehicle dependence. The research team examines the understudied implication 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 market conditions. The researchers conclude that TIAs likely have negative effects on urban housing production and affordability.

Related Publications

published journal article

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

policy brief

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

policy brief

Are Accessibility Evaluation Tools Ready for Prime Time?

published journal article

Tools of the Trade? Assessing the Progress of Accessibility Measures for Planning Practice

other

Is Accessibility Evaluation Ready for Prime Time?

published journal article

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

Publication Date

June 21, 2021

Associated Project

Areas of Expertise

From Traffic Impact Analysis to Accessibility Impact Analysis: Developing and Testing a Next Generation Development Impact Analysis Tool

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.

Related Publications

other

Working Paper: How Does Traffic, or the Fear of it, Affect Housing Affordability? Examining the Effect of Traffic Impact Analysis on Housing Production and Affordability

policy brief

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

policy brief

Are Accessibility Evaluation Tools Ready for Prime Time?

published journal article

Tools of the Trade? Assessing the Progress of Accessibility Measures for Planning Practice

other

Is Accessibility Evaluation Ready for Prime Time?

policy brief

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

Publication Date

August 1, 2021

Associated Project

Author(s)

Hao Ding, Brian D. Taylor

Areas of Expertise

Sources of and Gaps in Data for Understanding Public Transit Ridership

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.

Related Publications

other

Working Paper: How Does Traffic, or the Fear of it, Affect Housing Affordability? Examining the Effect of Traffic Impact Analysis on Housing Production and Affordability

published journal article

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

policy brief

Are Accessibility Evaluation Tools Ready for Prime Time?

published journal article

Tools of the Trade? Assessing the Progress of Accessibility Measures for Planning Practice

other

Is Accessibility Evaluation Ready for Prime Time?

policy brief

Sources of and Gaps in Public Transit Ridership Data

Publication Date

January 1, 2021

Associated Project

Author(s)

Jacob Wasserman, Brian D. Taylor

Areas of Expertise

Public Transit, Shared Mobility, & Active Transportation

Assessing the Safety Implication of AlternativeSpeed Limits in California

Abstract

Public transit in the United States is ailing. Before the COVID-19 pandemic, transit ridership fell by more than 800 million annual transit trips, or about 7.5%, between 2014 and 2019. The onset of the COVID-19 pandemic in the spring of 2020 only compounded these losses. Both before and during the pandemic, the changes in transit ridership were uneven, varying across metropolitan areas, built environments, times of day, days of the week, trip purposes, operators, modes, and directions.With high-quality, accessible, up-to-date data, practitioners and researchers can diagnose the causes of America’s transit ridership woes, as well as evaluate and recommend possible cures. The availability of detailed transit data, disaggregated across a number of axes, is more important than ever to the recovery of the transit industry and the mobility of those who rely on it. Moreover, data about transit use can answer pressing questions beyond patronage declines, including analyses of transportation equity, evaluations of proposed capital and operating improvements, inquiries into the effects of private shared mobility services, and projections of emissions and pollution, among others. All of these topics rely on a growing — though still incomplete and often incompatible — set of transit data sources collected in different ways, from different sources, on different timeframes

Related Publications

research report

Sources of and Gaps in Data for Understanding Public Transit Ridership

policy brief

Raising Truck Speed Limits in California Could Increase Mobility But May Also Increase Crashes

Publication Date

January 1, 2021

Associated Project

Author(s)

Michael Zhang, Sarder Rafee Musabbir

Areas of Expertise

Safety, Public Health, & Mobility Justice

Induced Travel Calculator Technical Assistance

Abstract

Highway speed limits inherently represent a tradeoff between safety and mobility. While higher speed limits shorten travel times and foster economic benefits (especially for the trucking and logistics industries), they can also increase the likelihood and severity of crashes, as higher vehicle speeds require longer stopping distances and generate more energy during a collision. Highway speed limits are increasing nationwide. While there is no consensus on the optimal speed limit (Figure 1), research generally shows that lower speed limits reduce the frequency and severity of crashes. Likewise, there is mixed evidence on whether a universal speed limit (trucks and passenger vehicles subject to the same speed limit) or a differential speed limit (trucks subject to a lower speed limit than passenger vehicles) is safer. While some evidence indicates that setting lower speed limits for heavier trucks that are slow to stop has safety benefits, other research suggests that differential speed limits create bottlenecks that may actually cause more crashes as cars attempt to overtake slower trucks. California is one of only seven states that set differential speed limits.

Related Publications

research report

Assessing the Safety Implication of Alternative Speed Limits in California

policy brief

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

Publication Date

January 1, 2021

Associated Project

Author(s)

Amy Lee, Jamey Volker, Susan Handy

Areas of Expertise