National Academies Press: OpenBook

Roadway Cross-Section Reallocation: A Guide (2023)

Chapter: Chapter 1 - Introduction

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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
×
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
×
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2023. Roadway Cross-Section Reallocation: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/26788.
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1-1   Introduction A Safety-First Approach to Allocating Roadway Space Streets make up more than 80% of public space in cities and towns. Who gets to use this space and how they can use it affects a community’s mobility, safety, economy, and quality of life. Com- munities around the world are discovering they can redefine the way streets work. Planners, engineers, and community groups are coming together to decide how they want to allocate this precious resource. These street transformations can affect people’s lives profoundly (Figure 1-1). Street transfor- mations can improve safety for people traveling along and across the street, stimulate sales for nearby businesses, reduce air pollution and carbon emissions, and improve the experience of people traveling by all modes. This Guide presents a process for making community-minded decisions about street design, describes how street-design decisions affect communities, and clarifies how different street ele- ments influence not just transportation outcomes, but livability, economic and environmental health, equity, and many other concerns. The Guide includes a framework that offers practi- tioners a straightforward way to consider all these community goals and choose a street cross section that serves everyone. The Changing Paradigm Change can be hard. People may struggle to imagine a street looking and working dif- ferently. Reallocation projects can become mired in the community engagement process as people worry about what the changes may mean for their businesses, their commutes, and their quality of life. Often not enough is known about exactly how a street-design change may affect people. This Guide seeks to address these issues. It details what is known about the effects of realloca- tion projects, connects cross-section decisions to outcomes, and introduces a way for making decisions that reflect community goals. Most important, this Guide puts safety, for all users, at the forefront of the decision-making process. Traditionally, street-design decisions have put the needs of drivers first. This attitude is so ingrained that whether a potential street design “works” is automatically measured against a thresh- old of vehicle delay that may not even be clearly stated. With so many standardized measurements of vehicular traffic flow built into performance metrics for streets and so few for livability, safety, health, accessibility, and comfort, traffic speeds and volumes are often prioritized by default. In recent years, communities and practitioners C H A P T E R 1

1-2 Roadway Cross-Section Reallocation: A Guide worldwide have responded by making a deliberate effort to consider the land-use context and the needs of all transportation system users when making decisions about street design. This Guide builds on that paradigm shift. It is also consistent with the Federal Highway Admin- istration’s (FHWA) Safe System approach, which promotes infrastructure design forgiving of human error for all road users. Reducing speeds and simplifying driver decision-making lowers the risk of severe injury or death in the event of a collision. Understanding the Tradeoffs With street space at a premium, tradeoffs are inevitable. This Guide supports practitioners in making decisions that reflect an explicit understanding of the different options for using this scarce resource. Every element in a street cross section is a choice, and each choice comes with consequences, both positive and negative. The Guide’s framework tool is built on the understanding that the public right-of-way is for everyone and that transportation affects people and communities in many ways. By better understanding the relationship between street design and other factors not typically associated with transportation, decisionmakers can establish performance measures and design criteria that better meet community goals. In this way, the Guide supports direct and objective con- versations about street design among transportation professionals, decisionmakers, and the community. Communicating Clearly About Vehicle Lane Removal Removing a lane for cars and trucks to make room for other uses can raise concerns in the community about congestion and delay. The tools commonly used today to screen for potential effects of roadway reallocation projects focus on worst-case automobile traffic conditions. This approach often limits conversations about cross-section ideas to whether effects are acceptable for drivers. In addition, traffic analysis tools usually only capture average delays during the time of day with the most traffic. This does not give people a good idea of what traffic is like through- out the day. The Decision-Making Framework introduces a new method for understanding the rela- tionship between cross-section changes and vehicle capacity. This new method measures how removing a travel lane affects traffic throughout the day, moving beyond the benchmark of whether a project “works” operationally outside the peak period. Understanding what delays and travel times will look like throughout the day will enable decisionmakers, stakeholders, and community groups to better understand the likely tradeoffs. Source: flickr.com/NYC_NYCDOT Figure 1-1. Separate spaces for people walking, biking, and driving on Allen St. in New York City.

Introduction 1-3   Raising the Floor on Safety As with everything else, the goal of safety results in tradeoffs. Despite transportation agencies’ focus on safety, tradeoffs may result in street designs that are unsafe for some users. Although communities understand that mobility is important and that it may be desirable for some streets to serve vehicles driving at speeds where a crash could result in a fatality, it is also important to recognize that it is a choice to design a street this way—one that we may have too readily accepted. This Guide seeks to “raise the floor” for safe street design by establishing minimum safe designs for each street element and articulating what a truly safety-first approach means in practice. For example, just as minimum lane widths are accepted as a safety need for drivers, context-sensitive safety considerations for other people using streets should also be routine. Community priorities may result in a design that does not meet minimal safety require- ments; however, with a safety-first approach, the cross-section development should not result in designs known to be unsafe or include elements that discourage travel on foot or by bike. This Guide’s purpose is to make the goal of designing safer streets for everyone the norm, rather than the exception. Making Decision-Making Transparent The influence of traffic operations in street-design decision-making is seldom acknowledged. The assumption that designs must minimize delay for motorists is so entrenched that ideas with significant positive effects on other aspects of street performance are often quickly dismissed without thoughtful analysis. A street design that reduces traffic capacity too much is proclaimed to “not work.” In other cases, separated bike lanes on streets with numerous travel lanes and parking lanes are said to “not fit.” The default (and often unstated) standard is that certain levels of motor vehicle delay are unacceptable, regardless of the life-saving benefits. Similarly, street-design projects aiming to increase traffic capacity often cite improved safety as an outcome to be achieved by reducing vehicle congestion. Not only are the safety benefits for drivers overstated, but these designs also—by increasing vehicular speed and exposing vulner- able road users to conflicts with drivers—make streets less safe for people walking and bicycling. The full explanation for these impressions, rarely expressed directly even if widely accepted, is that keeping motorized traffic flowing is a higher priority for a public agency than safety. For example, parking may be more important to a community than safety on a given street. If this is the case, the transportation agency and local government need to (1) be transparent about this prioritization and the corresponding tradeoffs and (2) confirm community buy-in. This Guide clarifies the rationales behind decisions. By fostering transparency, the Guide will help transportation practitioners compare tradeoffs and facilitate productive community con- versations about how to allocate public space and make street-design decisions. Connecting Decisions to Outcomes Although the traffic and safety effects of design decisions are well researched and understood, research on broader effects is still emerging. Transportation decisions directly affect public health, social equity, livability, the economy, and the environment. But the difficulty in quantify- ing these effects limits practitioners’ ability to incorporate them into an existing decision-making process that focuses on motor vehicle throughput and delay.

1-4 Roadway Cross-Section Reallocation: A Guide This Guide connects street cross-section design decisions to broader outcomes. Chapter 7 and Appendix B provide a comprehensive collection of research on these outcomes tied directly to cross-section elements. Practitioners can compare cross-section alternatives against community goals and priorities to select a preferred design. Traffic operations are just one of several potential impact areas, and the Guide enables practitioners to compare those effects with others. To help practitioners understand holistic traffic operations tradeoffs, the Guide provides a simplified tool to estimate the traffic capacity of street cross sections. Because traffic capacity is mostly determined at intersections, the Guide relies on planning-level traffic volumes and roadway configurations to estimate effects. Conventional traffic operations analyses focus on ideas of peak traffic conditions and encourage street designs with extra space for traffic, contributing to overbuilt conditions that may encourage speeding when traffic volumes are lower. This Guide presents an all-day perspective of traffic capac- ity and encourages practitioners to consider designs that balance the needs of drivers and other users at all times of the day. Using This Guide This Guide is designed to support practitioners throughout a cross-section reallocation project—whether a quick resurfacing and restriping opportunity or a full corridor reconstruction. The Guide provides information on the effects of cross-section decisions and helps practitioners weigh tradeoffs. At the core of this process is the Decision-Making Framework (presented in detail in Chapter 2). The Guide is accompanied by a spreadsheet tool (available at the National Academies Press website [nap.nationalacademies.org]) that walks practitioners through the decision-making process, incorporating the data and information presented throughout the Guide. The Guide is organized sequentially to provide insight into the decision-making process (Figure 1-2). Each chapter is useful as an individual resource, and readers should review the Figure 1-2. Cross-Section Decision-Making Framework.

Introduction 1-5   material linearly at least once. After that, practitioners may review different steps of the process as needed. Key terms or terms that may not be familiar to readers are defined in the Glossary. The remainder of the Guide takes the reader through each of the Decision-Making Frame- work’s steps and is organized as follows: • Chapter 2, Choosing a Roadway Cross Section That Serves Your Vision, introduces the Decision- Making Framework and describes the principles on which the framework is built. • Chapter 3, Opportunities to Change a Cross Section, summarizes how to evaluate the needs of a street, including how a street’s context and function inform cross section decisions. • Chapter 4, Planning Context, describes how street design affects communities and identifies opportunities to use cross-section reallocation to meet broader goals. • Chapter 5, Safety for Everyone, explores the foundational principle that streets should be designed to be at least minimally safe for all modes. • Chapter 6, Overcoming Barriers to Safe Design, offers strategies for achieving safe designs when other priorities compete for the limited right-of-way. • Chapter 7, Cross-Section Elements, provides detailed information on the most common types of cross-section elements, including information on how these elements affect broader com- munity goals. • Chapter 8, Making and Evaluating Cross-Section Changes, presents strategies for implement- ing cross-section changes and suggests evaluation methods for improving future designs. This chapter also includes findings from a selection of cross-section reallocation case studies com- pleted in recent years. • Appendix A, Cross-Section Decision-Making Tool and User Guide, provides detailed instruc- tions on using the Cross-Section Decision-Making Tool, including illustrations and references to relevant information in the Guide. • Appendix B, Decision Support Matrix, documents the relationships between cross-section changes and outcomes, including safety, economy, environment, social equity, and mode shift. • Appendix C, Applying the Framework, demonstrates applying the decision-making process to a sample project.

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Streets make up more than 80 percent of public space in cities and towns. From one edge of the right-of-way to the other, planners, engineers, and community groups are coming together to decide how they want to allocate this precious resource.

NCHRP Research Report 1036: Roadway Cross-Section Reallocation: A Guide, from TRB's National Cooperative Highway Research Program, describes how street design decisions impact communities and clarifies how different street elements influence not just transportation outcomes, but livability, economic and environmental health, equity, and many other concerns.

Supplemental to the report are NCHRP Web-Only Document 342: Roadway Cross-Section Reallocation: Conduct of Research Report and two Decision-Making Spreadsheet Tools, one on Reconstruction and another on Repaving.

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