Beyond Theory: Evolution, Benefits, and Evaluation Challenges of Complete Streets Policy in the United States

Abstract

The Complete Streets policy has gained popularity in recent decades. This paper traces the evolution of the policy in the United States by reviewing the relevant literature. It examines the conceptual framework, objectives, and design requirements, followed by the state of practice, implementation, evolution, and anticipated benefits of the policy, such as its impact on transportation, travel behavior, safety, health, environment, and economy, and how these benefits have been quantified. The study identifies research gaps in evaluating the success of the Complete Streets policy. The insights gained can help policy and decision-makers, aid implementation, and promote sustainable transportation and urban planning at various scales.

1. Introduction

The Complete Streets movement has emerged to promote transportation design that serves all users, shifting the focus from cars to a more inclusive approach that supports every mode of travel [1]. The Complete Streets policy is broadly defined as a street design framework that accommodates all road users, regardless of their mode of travel or ability [2]. In addition to its transportation benefits, the policy is expected to have social, environmental, safety, and economic benefits as well [3]. The key objective of Complete Streets is to reduce the dominance of motorized transportation while facilitating the movements of pedestrians and cyclists. This approach makes the Complete Street a versatile public space that can be used for a range of activities beyond just transportation mobility and accessibility [4].

Complete Streets transportation plans have been implemented in many cities across the country to prioritize pedestrians, cyclists, and transit users in construction and design. While planning authorities are trying to address the needs of different communities and travelers by supporting legislation that would require prioritizing multi-modal transportation options, providing interconnectivity of all modes and travel options, system preservation, and innovation for convenient travel, the planning and implementation of Complete Streets can be challenging. The process is best supported by using empirical evidence based on reliable, highly granular data and enhanced modeling tools. The success of Complete Streets implementation projects depends on future demands for alternative modes of transportation and on the development of compact, residential/commercial, multi-modal urban neighborhoods.

To evaluate the performance of Complete Streets, it is necessary to forecast the level of demand for these alternative travel options in neighborhoods across the state. However, existing studies on methods, models, and tools to evaluate the performance of Complete Streets projects are limited. To address this gap, this study provides a comprehensive review of the literature on the Complete Streets policy’s impact on transportation systems, focusing on travel behavior, safety, economy, environment and health. Specifically, we aim to answer the following questions:

• How has the Complete Streets policy framework evolved in the United States, and what are its foundational objectives and design principles?
• In what ways have Complete Streets policies been implemented across U.S. and what design and planning approaches are used in current practice?
• What are the impacts of Complete Streets across transportation, environment, safety, health, and economic domains, and how are these impacts operationalized and measured?
• What methodological approaches are employed to evaluate the effectiveness of Complete Streets, particularly regarding their influence on travel behavior and mode choice decisions?

To answer these questions, we conducted a systematic search and screening of the literature following the PRISMA method [5]. Specifically, we used key terms and phrases in two databases: Google Scholar and Scopus. The specific search terms we used are: “Complete Streets” and “Health Impacts”, “Complete Streets” and “Economic Impacts”, “Complete Streets” and “Travel Behavior”, “Complete Streets” and “Environmental Impacts”, “Complete Streets” and “Measuring Performance “, “ Complete Streets” and “Impacts”, “ Complete Streets” and “Benefits”, “Complete Streets” and “Project Outcomes”. We chose these two databases for their complementary strengths. Google Scholar provides broad coverage, including grey literature and interdisciplinary sources, while Scopus offers high-quality, peer-reviewed content with robust citation tracking. Using both ensures a comprehensive and credible literature review. The screening included research reports and scientific papers published in peer-reviewed journals and conferences, as well as databases that may contain relevant information without any restriction on publication date or method of analysis. Through this process, described in Figure 1, a total of 1294 records were identified through database searching. After removing 352 duplicates, 942 records remained for screening. Following the title and abstract screening, 744 records were excluded, leaving 198 full-text articles for eligibility assessment. Of these, 92 articles were excluded for reasons such as not meeting inclusion criteria or lacking relevant data, leaving 106 full-text articles for analysis. As a complementary approach, we also used the forward and backward snowballing technique to find any additional articles that were not included in our database search. Ultimately, 145 full-text studies were included in the final qualitative synthesis.

From the articles we found, we selected a subset that falls into one of the four categories to address our research questions: (i) Complete Streets concept, objectives, and design requirements, (ii) state of the practice in design and implementation examples from the US, (iii) expected benefits in terms of transportation, environmental, safety, health, and economic impacts and how they are measured, (iv) methods for evaluating Complete Streets performance with an emphasis on transportation/travel behavior impacts focusing on mode choice decisions.

The insights gained in terms of the various evaluation metrics for the success of the policy, in addition to the research gaps discussed in this study, will help policy and decision-makers and local/regional government officials across the country better implement, maintain, and evaluate their Complete Streets policy as an effective tool to promote and achieve sustainable transportation and urban planning at both local and regional scales.

To present our comprehensive review systematically, this paper is organized into five sections. Section 2 summarizes the conceptual framework, main objectives, and design requirements of the Complete Streets policy, as documented in previous studies. Section 3 documents and discusses the current state of practice of the policy, elaborating on its implementation and support in hundreds of cities and jurisdictions across the country within the last few decades, and how the design and implementation steps have evolved over time. In Section 4, we discuss the expected benefits and outcomes of the Complete Streets policy in terms of transportation, environmental, safety, health, and economic impacts, and how these impacts were measured and evaluated in the literature. Finally, the last section identifies and discusses the main research gaps in the existing methods for evaluating Complete Streets’ performance, with a focus on transportation and travel behavior impacts, especially mode choice decisions.

2. Background: Conceptual Framework and Policy Design Elements

The Complete Streets policy aims to promote transportation equity for all users, including pedestrians, bicyclists, motorists, and transit riders of all ages and abilities [6]. Complete Streets are designed and operated to enable safe access for everyone, especially those considered “transportation-disadvantaged,” including racial minority groups, low-income populations, people with disabilities, the elderly, and the youth. These groups often lack easy access to transportation options, healthy food, medical care, and employment/educational opportunities, making it crucial to provide accessibility to alternative transportation options that are fast, safe, convenient, and affordable [7,8,9].

Research shows that millions of Americans who are unable to drive due to physical restrictions remain homebound due to a lack of viable transportation alternatives, particularly those who are aged 65 and over [10]. Complete Streets can help reduce the environmental barriers that discourage alternative transportation modes and ultimately accommodate all users, regardless of their socio-demographic status, physical abilities, and preferences. As Litman [3] stated, “this integrated planning makes travel without a car convenient, comfortable, and affordable while creating communities where households own fewer vehicles, drive less, and rely on alternative modes.”

Numerous studies have highlighted the importance of Complete Streets in attracting more transportation-disadvantaged users to the streets [11,12,13,14]. By providing safe and accessible transportation options, Complete Streets promote equity and foster healthier, more vibrant communities.

Over the years, private automobiles have been prioritized in urban transportation system design/planning, leading to the construction of miles of roads and highways. In many cases, urban arterials have been engineered to accommodate cars while pedestrians are left with minimal facilities, and bus stops are mere poles next to high-speed traffic [15]. In contrast, Complete Streets design aims to support all active users, including pedestrians, while accommodating automobiles. The design intends to make multimodal accommodations without requiring extra time or funds [16,17].

Although the popularity of the Complete Streets policy has increased in the past few decades, the foundation for such a policy was laid out over 50 years ago. The first Complete Streets-related policy was adopted in Oregon in 1971, though it was not referred to as “Complete Streets” at the time. The policy emphasized infrastructure and support for alternative modes of transportation, stating that “footpaths and bicycle trails, including curb cuts or ramps as part of the project, shall be provided wherever a highway, road, or street is being constructed, reconstructed, or relocated.”

Between 1971 and 1999, only a few policies across the country addressed multimodal accommodation. However, between 2000 and 2003, the number of policies and programs doubled. The term “Complete Streets” was officially coined in December 2003 to promote inclusivity of pedestrians, public transit riders, and other road users [18]. In 2005, the National Complete Streets Coalition (NCSC) was established as a non-profit, non-partisan collaborative effort to advocate for the policy at all federal, state, and local levels [2]. Between 2008 and 2010, the number of Complete Streets policies doubled annually. By 2010, nearly half of the U.S. states had integrated Complete Streets principles into local or statewide transportation policies [19]. Today, over 1000 jurisdictions across the United States have adopted some form of Complete Streets policy, promoting non-motorized transportation and transit through street design and built environment modifications [16,17,19,20,21,22].

The term “Complete Streets” encompasses a variety of tools, concepts, and elements designed to improve social, economic, and environmental outcomes along urban road corridors [23]. While transportation professionals primarily use this term, other professionals from different disciplines use related terms such as “Smart Growth” (regional planners) and “Transit-oriented Development” or “New Urbanism” (local planners), which share the same conceptual framework and features and are often used interchangeably. Although “Complete Streets” is a relatively new term, many of its associated elements and the primary concept have existed for a long time.

The Complete Streets concept focuses on three main areas: (1) diverse modes of transportation, such as walking, cycling, public transit, and automobiles; (2) different types of users, including low-income individuals, affluent individuals, senior citizens, and people with disabilities; and (3) a mix of land uses, including retail, businesses, residential, and office spaces, to ensure that streets are safe, balanced, and inclusive to support a variety of economic, cultural, and environmental uses [10,15,24,25,26]. Successful Complete Streets projects prioritize and encourage multi-modal transport systems to promote livable communities, equity, economic development, reduced crashes and injuries, and improved public health. In other words, successful Complete Streets projects must ensure that roads serve diverse functions, including mobility, commerce, recreation, and community cohesion, and that road users have multiple mode choices, including non-motorized modes and well-connected public transit options [3,27].

Achieving Complete Streets (or transitioning from mobility-based to accessibility-based designs) using a cost-effective approach requires collaboration among traffic engineers, planners, policymakers, and the general public [28,29]. The approach involves not only modifying individual roads but fundamentally changing the decision-making and design process so that all users are considered in every stage of development, from planning and construction to maintenance and operation [15,30,31].

While there is no uniform or standardized format for implementing Complete Streets, the [2] recommends considering the following factors in a comprehensive policy framework:

• Vision: The policy establishes a motivating vision for why the community wants to have Complete Streets: for improved safety, better health, increased efficiency, convenience of choices, or other reasons.
• Intent: The policy intents need to be clearly written to specify the goals and changes needed to fulfill the policy’s intent.
• All users and modes: The policy specifies that “all modes” includes walking, bicycling, riding public transportation, driving trucks, buses, and automobiles, and “all users” includes people of all ages and abilities.
• All projects and phases: All types of transportation projects are subject to the policy, including design, planning, construction, maintenance, and operations of new and existing streets and facilities.
• Clear, accountable exceptions: Any exceptions to the policy are specified and approved by a high-level official.
• Network: The policy recognizes the need to create comprehensive, integrated, and connected networks for all modes and encourages street connectivity.
• Jurisdiction: All other agencies that govern transportation activities can clearly understand the policy’s application and may be involved in the process as appropriate
• Design: The policy recommends use of the latest and best design criteria and guidelines, while recognizing the need for flexibility to balance user needs
• Context sensitivity: The current and planned context, i.e., buildings, land use, and transportation needs, is considered in planning and design solutions for transportation projects.
• Performance measures: The policy includes performance standards with measurable outcomes.
• Implementation steps: Specific next steps for implementing the policy are described in the policy.

Various studies have discussed the conceptual framework and best practices of Complete Streets policies, providing insights for planners and transportation professionals on policy requirements, design elements, evaluation criteria, project costs, and more, to achieve more efficient design and implementation of this policy [1,32,33,34]. The common elements used in most Complete Streets projects include wide sidewalks, frequent and safe crossings (e.g., median islands, accessible pedestrian signals, curb extensions), bicycle lanes (or wide, paved shoulders) and bicycle parking, shared-use paths, road diets, traffic calming measures to lower automobile speeds and define the edges of automobile travel lanes, greenery design, and public transit accommodations (e.g., accessible transit stops, bus shelters, dedicated bus lanes), among other features [25,35,36].

Table 1. The main features of Complete Streets design.

Pedestrian/Bike Infrastructure	Traffic Calming	Public Transit Accommodations
Sidewalks, or wide paved shoulders Frequent and safe crossing opportunities Accessible pedestrian signals Bike lanes	Median islands Narrower travel lanes Roundabouts Curb extensions	Special bus lanes Comfortable and accessible stops

categorizes some of the most significant and common features of Complete Streets design used in hundreds of projects nationwide into three main groups based on the types of users, including pedestrian and bicycle infrastructure, traffic calming, and public transit accommodations.

When communicating with advocates and policymakers, it is important to understand the specific factors that influence the growth and expansion of Complete Streets policies. Moreland-Russell, Eyler [19] analyzed data from 49 community-level policies and identified several factors that could affect the rate of Complete Streets policy diffusion, including rural/urban status, state obesity rate, state funding for transportation, state obesity prevention funding, percentage of commuters who walk or bike to work, presence of a state Complete Streets policy, and the number of bordering communities with some form of Complete Streets policy. Among these factors, the study found that state obesity rate, percentage of commuters who bike or walk to work, and the presence of a border community with a Complete Streets policy were the most significant variables influencing the adoption of Complete Streets policies in each state.

Several studies have analyzed the cost–benefit of Complete Streets projects to determine their economic feasibility. Shapard and Cole [34] conducted a case study in the City of Charlotte, North Carolina, to estimate the cost range of typical Complete Streets projects and compared it to the cost of building a traditional street. Their findings indicated that incorporating Complete Streets elements slightly increases the cost of a project, with an increase of as little as 5% of the overall project budget for a four-lane divided street. However, the additional investment in Complete Streets design and implementation is a long-term investment in the financial and physical health of the community. Although it is difficult to monetize the value added to the cities and residents’ quality of life due to increased walkability, safety, and congestion relief, it is widely recognized that Complete Streets projects have significant benefits that are not easily quantifiable [34,37,38]. Moreover, Complete Street projects are significantly less expensive than conventional transportation projects, both in terms of normal-cost and high-cost per mile specified by the Federal Highway Administration’s estimates, while they yield significant safety results [27,32].

The concept of complete streets is highly dependent on context, as noted by many researchers. This means that there is no single approach to achieving completeness and that the methods used will vary depending on the specific environment, location, and other factors. In some situations, it may not even be necessary to accommodate all modes of transportation to create a complete street [25,37,39]. Understanding the context-specific nature of Complete Streets sets the stage for examining how these policies are interpreted and applied in practice. The following section explores the roles that federal and state governments play in shaping, guiding, and supporting the design and implementation of Complete Streets initiatives.

3. State of the Practice: Federal and State Government Roles in Complete Streets Policy Design and Implementation

The federal government actively encourages state governments to incorporate the design concepts associated with Complete Streets policy, despite the lack of legislative mandate at the Federal level. The Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991 was the first step towards this goal, followed by several supporting acts, such as Transportation Equity Act for the 21st Century (TEA-21) in 1998, Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) in 2005, USDOT Policy Statement on Bicycle and Pedestrian Accommodation Regulations and Recommendation in 2010 (https://www.fhwa.dot.gov/environment/bicycle_pedestrian/guidance/policy_accom.cfm) (accessed on 30 October 2025), and the Moving Ahead for Progress in the 21st Century Act (MAP-21) in 2012 [30,40]. In 2008, a few Federal bills were introduced in Congress, such as HR 5951: Safe and Complete Streets Act of 2008 and S2686: Complete Streets Act of 2008, but none passed. Several years later, the House of Representatives approved the Comprehensive Transportation and Consumer Protection Act of 2015, a six-year Complete Streets bill requiring states and MPOs to accommodate the safety and convenience of all users in all federally funded projects. As a result, the Federal Highway Administration proposed revisions to its rule governing design standards for the National Highway System (NHS) to accommodate Complete Streets design standards. The NHS includes interstates and other high-speed, high-volume roads, as well as arterial routes serving commercial centers, homes, shops, parks, schools, and hospitals—places where people often walk, bike, or take public transportation, in addition to driving. In September 2019, California passed the “Transportation funding: active transportation: Complete Streets” act, mandating the inclusion of Complete Streets design elements and prioritization of safe and connected facilities for pedestrians, bicyclists, and transit users on all State Highway Operation and Protection Program projects and asset management plans (https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201920200SB127) (accessed on 30 October 2025).

According to the National Complete Streets Coalition (NCSC), more than half of American states have adopted explicit state-level policies to encourage the adoption of Complete Streets. Many of these states have strengthened their commitment to Complete Streets by supplementing their initial policies with additional laws or executive orders, resulting in greater comprehensiveness [41].

For example, in October 2008, the California Department of Transportation revised its policy directive for bicyclists’ and pedestrians’ use of state highways with a new policy called “Complete Streets—Integrating the Transportation System,” which considers local context. Additionally, Complete Streets is included as one of the strategies in the California Air Resources Board’s Climate Change Scoping Report. The objectives of these policies and acts are to promote active transportation modes such as walking and cycling, reduce private and public transportation costs, and create safe and livable communities on a local level [42].

In January 2009, Hawaii introduced Complete Streets and Safe Routes to School (SRTS) legislation, and in 2008, Illinois passed a law that requires the state department of transportation to accommodate bicycle and pedestrian travel on all its roads in urbanized areas. Other states, such as Oregon, Florida, Maryland, Missouri, and cities such as Arlington, VA, Honolulu, HI, Boulder, CO, and Kansas City, MO, have been designing and implementing Complete Streets for several years [43,44,45]. In Charlotte, North Carolina, transportation planners have adopted a six-step Complete Streets planning process that systematically evaluates the needs of all modes.

The NCSC provides assistance to local jurisdictions in planning, implementing, and facilitating multimodal street design policies through its Local Implementation Assistance Program [15]. Estimates by Carlson, Paul [46] suggest that 25.2% of municipalities in the United States have Complete Streets policies, with higher prevalence in larger municipalities (49.6% in those with ≥50,000 people). Smart Growth America reports that cities and metropolitan areas in over 36 states and territories have implemented Complete Streets projects and plans, guiding local transportation agencies to prioritize pedestrians, cyclists, and transit users in construction and design principles (see Figure 2). Gregg and Hess [47] analyzed a sample of 113 municipal-level CS policies focusing on their qualitative content, e.g., definitions, and their implications for design and implementation. The analysis revealed that policies are broad and do not ensure accommodating all user types equally.

4. Complete Streets Implementation, Benefits and Evaluation of Success

Evaluating the completeness of streets and their impacts on transportation systems, community development, and the economy can provide valuable insights for infrastructure investment and planning policy. A context-sensitive framework for quantitatively defining the completeness of a Complete Street by measuring its various impacts is useful in planning and design [39,48,49]. To fully analyze the benefits of Complete Streets policies, it is important to consider their impacts on transportation (including multimodal level of service, behavior, and safety), the environment, the economy, and health [35,39].

While most of the Complete Streets literature focuses on evaluating the qualitative goals of the policy and its design elements through the analysis of projects across the country, there has been less scholarly attention paid to quantitatively assessing and measuring the performance of existing projects and their various effects, particularly on transportation and travel behavior. The extensive body of literature on the interaction between the built environment and travel behavior does not specifically address the impacts of Complete Streets implementation, and there is a lack of comprehensive and rigorous research on the social, behavioral, economic, and environmental impacts of Complete Streets. However, some detailed research has been done on a street-by-street or link-by-link basis, focusing on the travel behavior and safety benefits of more livable streets [32].

To ensure proper implementation and evaluate the success of Complete Streets projects, it is essential to use performance measures. Smart Growth America [50] emphasizes the need for continuous evaluation of the success of Complete Streets projects, and they provide the following performance measures to assess factors such as mode shift, safety, accessibility, and economic vitality:

• User data–bike, pedestrian, transit, and traffic
• Crash data
• Use of new projects by mode
• Compliments and complaints
• Linear feet of pedestrian accommodations built
• Number of ADA accommodations built
• Miles of bike lanes/trails built or striped
• Number of transit accessibility accommodations built
• Number of street trees planted

More recently, Dehghanmongabadi and Hoşkara [51] also developed a framework to evaluate and measure the success of Complete Streets through consideration of both physically and socially inclusive variables. To this end, they listed variables in land-use, community design, socioeconomic and demographic, and community attitude categories.

Although every design or redesign is unique, Complete Streets are associated with several key benefits, including social, environmental, health, and economic benefits, which are interconnected to some extent [32]. For instance, implementing the policy can lead to changes in travel behavior, resulting in increased physical activity levels that are linked to various public health benefits, as demonstrated by multiple studies [52,53,54,55,56,57]. These health outcomes could, in turn, lead to substantial economic benefits through cost savings. Furthermore, Complete Streets are associated with enhanced safety for motorists and other users, primarily due to reduced vehicular travel speeds, as well as reduced air and noise pollution [58,59]. By creating more active, accessible, and appealing environments, Complete Streets are anticipated to enhance livability and economic activity and foster healthier lifestyles for residents [37,60]. A study that analyzed several individual Complete Streets projects nationwide found that most projects led to decreased crash rates and increased rates of pedestrian, bicycle, and public transit trips when rates before and after the projects were compared. These projects were also less expensive per mile than typical arterial projects [27].

Studies have shown that Complete Streets modifications to roadways are desirable for users of different modes, including drivers [28].

Table 2. Potential Benefits and Costs of Complete Streets (Source: [3]).

	Improved Transport Options	Increased Use of Alternative Modes	Reduced Automobile Travel	Smart Growth Development
Potential benefits	- Improved user convenience & comfort - Improved accessibility, particularly for non-drivers - Option value - Increased local property values	- User enjoyment - Improved public fitness and health - Increased community cohesion (positive interactions among neighbors due to more walking on local streets)	- Reduced congestion - Road and parking savings - Consumer savings - Reduced crashes - Reduced chauffeuring burdens - Energy conservation - Reduced air & noise pollution	- Improved land use accessibility - Transport cost savings - Infrastructure savings - Open space preservation - Improved aesthetics - Urban redevelopment - Support for local businesses
Potential costs	- Planning and implementation - Lower traffic speeds	- Additional user costs (shoes, bikes, fares, etc.)	- Reduced travel speeds - Reduced parking convenience	- Increases in some development costs - Transition costs

, adapted from Litman [3], presents the potential benefits versus costs of Complete Streets projects regarding improved transport options and use of alternative modes, reduced automobile dependency, and enhanced smart growth development. As shown, the potential benefits of Complete Streets projects outweigh the costs. Implementation of these projects would ultimately strive for more sustainable and livable transportation systems and communities. The following subsections summarize the benefits/impacts of Complete Streets policy, as studied in previous literature, regarding transportation and travel behavior, safety, economic development, environment, and public health.

4.1. Transportation and Travel Behavior Impacts

Complete Streets can provide numerous direct and indirect transport and community development impacts, including improved accessibility and safety for non-drivers, increased economic activity and local property values, energy conservation and emission reductions, lower traffic speeds, improved community livability and aesthetics, improved public transit service and mode shifts, improved public fitness and health, and support for strategic development such as urban redevelopment and reduced sprawl [3,35,39,61,62]. Literature suggests that in general, the various outcomes of Complete Streets intervention, such as perceived traffic and crime safety, pleasantness of walking, proximity to various amenities, such as shops, services, and transit stops due to land-use mixture, significantly promote non-motorized transportation for both traveling and recreational purposes [16,63,64,65]. However, despite all the transportation and behavioral impacts of Complete Streets policy, little research has been done to quantitatively measure and confirm these benefits and outcomes. Much of the relevant literature only focuses on descriptive analysis of improvements to the accessibility, travel speeds, and overall safety of all users [66]. Many studies have attempted to evaluate the performance of Complete Streets projects through completeness scores [48,49]. Kingsbury, Lowry [49] presented a four-dimensional audit for automobiles, transit users, bicyclists, and pedestrians to assess completeness and compare the balance between modes. Jordan, Ivey [67] developed a capability maturity model, adapting from an existing transportation-focused capability maturity framework to help agencies measure the maturity of their existing Complete Street programs and aid in strategic planning and organizational capacity building. The National Complete Streets Coalition has also emphasized the uniqueness of every street, making it almost impossible to provide a single description of completeness. As mentioned above, most of these analyses were more qualitative and planning-oriented, and, therefore, they are structured more towards a qualitative rather than a quantitative assessment of impacts.

Sugiyama, Neuhaus [64] conducted a study on the impacts of Complete Streets policy on transportation and found that proximity to retail shops, services, transit stops, and easy access to sidewalks were associated with increased utilitarian walking (walking to destinations). Meanwhile, recreational walking was associated with proximity to recreational destinations and route aesthetics. Slotterback and Zerger [36] provided a qualitative evaluation guidebook on the conceptualization and implementation of Complete Streets policy by studying best practices in various states, including Minnesota, Virginia, Colorado, North Carolina, Ohio, Iowa, North Dakota, Wisconsin, and Connecticut.

Elias [23] tested different design features of Complete Streets and their impact on pedestrian and bicycle Level of Service (LOS) scores compared to auto-oriented streets. The results showed that Complete Streets design can improve bicycle and pedestrian LOS while minimally affecting auto LOS. Carter, Martin [68] focused on LOS for multiple travel modes to address the need by agencies in their efforts to evaluate multimodal LOS methods’ sensitivity to inform transportation investments, including complete streets projects. They surveyed transportation professionals on the major factors affecting multimodal LOS (including pedestrian, bicycle, transit, and auto). They conducted sensitivity tests in four cities to measure the performance of the HCM 2010 [69] multimodal LOS scores based on the factors given by the survey respondents. The results were mixed, suggesting additional research on multimodal LOS methods.

Schlossberg and Rowell [70] documented the redesign of 25 streets across the United States and highlighted measurable outcomes of the redesign on traffic, safety, and economic measures. They found that cycling behavior improved significantly, and safety was improved with fewer and less severe accidents and crimes, decreased auto travel times, and increased transit ridership. Ferguson et al. [32] examined 15 street cases in the City of Hamilton to assess the effectiveness of Complete Street concepts and practices in shaping the city’s development. Brown et al. [71] studied the influence of Complete Streets on transit-related vs. non-transit walking and found that residents were more likely to walk if they lived near Complete Streets.

Previous research has extensively explored the effects of pedestrian- and transit-friendly transportation policies and programs on mode choice using advanced mode choice models. These studies indicate that improving access to alternative modes of transportation and enhancing their attractiveness, safety, and efficiency through various policies can lead to a shift towards non-motorized and transit mode choice [72,73,74,75,76,77].

Numerous studies have also investigated the effects of transit-oriented development and smart growth, terms often used interchangeably with Complete Streets, on travel behavior and sustainable mode choice [78,79,80,81]. However, literature specifically modeling travel behavior and mode choice changes resulting from Complete Streets interventions is limited. Among these limited studies that focus on the behavioral impacts of various Complete Streets design elements, some suggest that the influence is not uniform across all design elements, with certain elements heavily influencing mode choice while others have little or negligible impact [82,83,84].

These results suggest that evaluating the impacts of Complete Streets interventions on travel behavior requires careful study design, as changes may be influenced by broader socioeconomic trends, local land use developments, transit service modifications, and self-selection effects [85,86,87]. To better isolate the causal effects of the interventions, quasi-experimental approaches such as difference-in-differences analysis with matched control sites or synthetic control methods are critical for minimizing bias and confounding.

4.2. Safety and Community Impacts

Numerous studies have investigated the impact of Complete Streets design and policy implementation on the safety of pedestrians and bicyclists, consistently indicating that these interventions can increase pedestrian and cycling activity while reducing crash frequency and severity [15,27,33,88,89,90,91,92]. Complete Streets incorporate design elements that collectively improve safety for all users, e.g., pedestrians, cyclists, transit riders, and motorists. Research shows that narrower lanes and road diets slow vehicle speeds and reduce crash severity [15,82,93,94,95], while traffic-calming features such as speed humps, raised crossings, roundabouts, and curb extensions enhance safety at intersections and crossings [94,96,97,98,99]. Protected or clearly marked bike lanes lower cyclist crash risk and can reduce vehicle speeds by up to 28% [100,101,102]. Well-marked and signalized pedestrian crossings, combined with curb extensions and refuge islands, further improve visibility and crossing safety [15,82,96,103]. Improved lighting, landscaping, and reduced traffic volumes contribute to both real and perceived safety, particularly for vulnerable users such as children, older adults, and people with disabilities [82,100,103,104,105,106].

Empirical evidence supports these findings. For instance, Huang et al. [107] found that the percentage of crashes dropped by 6% after Complete Streets interventions in several California and Washington cities. Anderson et al. [27] reported that about 70% of the projects experienced reduction in collisions and injuries after their redesigns, while the New York City Department of Transportation documented a 40–50% reduction in total crash rates (pedestrians, cyclists, and motorists) after installing bike lanes on the city’s arterials [108]. Similarly, narrower streets with lower design speeds tend to have fewer and less severe accidents, while communities with more connected multimodal networks experience lower per capita crash rates [88,92]. Moreover, Complete Streets interventions in New York have been associated with a 16% reduction in pedestrian injury crashes and an 80% reduction in fatalities [96].

Marshall [109] also emphasized that multimodal street designs can significantly reduce traffic injury and fatality rates across U.S. cities. In one study, conversion of four-lane undivided roadways to three-lane cross-sections in typical Iowa towns reduced crash frequency by 25% and injuries by 34% [110]. Overall, the evidence demonstrates that design features such as narrower lanes, traffic calming, protected bike lanes, and enhanced crossings are among the most effective strategies for improving multimodal safety outcomes. However, collision rates alone do not fully capture the mechanisms behind these safety improvements, and crash data are often underreported in multimodal environments [27,111].

To address these limitations, Tolford et al. [91] proposed and piloted a low-cost methodology in New Orleans, Louisiana, for evaluating pedestrian safety within the context of Complete Streets policy implementation. Using a spatial tool, they identified areas with statistically significant pedestrian crash clusters and showed that many of these locations exhibited low pedestrian traffic volumes but substantial accessibility issues, such as insufficient curb ramps, inadequate street furniture, limited transit shelters, and narrow sidewalks. These findings suggest that systematic adoption of Complete Streets principles, particularly through road diets and similar design adjustments, can enhance accessibility for pedestrians, cyclists, and transit users and ultimately lower pedestrian crash rates.

In a more recent study, Mooney et al. [90] investigated the effect of Complete Streets policies on overall numbers of cyclist fatalities while accounting for potential policy effects on the size of the cycling population using cyclist fatality data between January 2000 and December 2015. They found that Complete Streets policies made cycling safer overall, averting 0.6 fatalities per 100,000 cyclist-years by encouraging a 2.4% increase in cycling but producing only a 0.7% increase in cyclist fatalities.

Beyond traffic safety and environmental benefits, Complete Streets initiatives have been associated with enhanced community cohesion and social inclusivity. They create public spaces that encourage social interaction, improve perceptions of neighborhood safety, and expand mobility options for populations often excluded from traditional street designs. Research has shown that more walkable and bike-friendly environments foster greater neighbor-to-neighbor interaction and collective efficacy [112], and that street designs prioritizing accessibility can help reduce mobility barriers for historically marginalized groups, including low-income populations, older adults, and people with disabilities, e.g., [113,114]. Additionally, programs like safe routes to school can be implemented in conjunction with Complete Streets frameworks, and can be associated with higher community engagement and perceptions of neighborhood safety [115].

4.3. Economic Development Impacts

In addition to the potential transportation and safety benefits of Complete Streets, many economic development benefits can be envisioned as well. Although limited research has focused on the economic benefits of Complete Streets, previous studies suggest that Complete Streets interventions could potentially bring about many positive economic changes, such as the creation of new businesses and employment opportunities, increased property values, and increased retail sales through changes in travel behavior [3,58,70,116]. However, the magnitude and distribution of these benefits vary by context. Studies indicate that property values near Complete Streets conversions rise by about 8–10.5%, with variation across neighborhoods [117,118,119]. These projects often spur private investment, higher tax revenues, and business growth through increased sales, new jobs, and enhanced local spending [66,120], while also contributing to higher household consumption and home improvements [119]. However, the economic gains are not distributed evenly, i.e., benefits frequently concentrate in advantaged or gentrifying areas, whereas lower-income or less walkable neighborhoods may see fewer gains or face displacement pressures [121,122]. The spatial variation in property value increases is substantial [117,122], and although some evidence suggests enhanced equity for women and pedestrians, overall distribution remains uneven and context-dependent [11,16,121].

When users of different modes and capabilities feel safer along a corridor, they are more likely to use it more frequently, which can enhance local economic vitality. These behavioral shifts can lead to increased foot traffic, higher retail sales, appreciation in nearby residential and commercial property values, and the attraction of new businesses. Several studies document these impacts, though the strength of the evidence varies based on methodological rigor.

In Lancaster, California, a ~$10.6 million Complete Streets-style investment known as the BLVD project resulted in approximately 50 new businesses, 800 permanent jobs, a 96% increase in business revenues, and a 9.5% rise in nearby property values [27]. However, these findings are based on a pre- and post-project case study without a control or comparison area, limiting the ability to attribute causality solely to the Complete Streets intervention. Broader economic trends in the region may have influenced outcomes.

Likewise, a before-and-after analysis by the NYC Department of Transportation [123] reported a 49% increase in retail sales following the redesign of 8th and 9th Avenues in Manhattan. In Brooklyn, a public plaza conversion on Pearl Street led to a 172% increase in nearby retail sales volume [124]. While these findings are significant, they also lack rigorous counterfactuals and do not account for other factors such as concurrent neighborhood investments or economic shifts.

More systematic evidence comes from a cross-case comparative analysis of 37 Complete Streets projects conducted by Smart Growth America [125]. Among the communities with available data, 8 out of 10 experienced increases in property values post-implementation. While this study offers a broader perspective, the data collection and reporting standards varied across locations, and the study did not use formal statistical controls to isolate causal effects.

To address such limitations, more rigorous methods have been employed in recent research. For example, a natural experiment study with propensity score matching by Yu et al. [118] in Orlando, Florida, found that single-family homes exposed to a Complete Streets project on Edgewater Drive had, on average, 8.2% higher home value appreciation during the housing market boom (2000–2007) and 4.3% greater resilience during the 2007–2011 recession, compared to homes in non-exposed control areas. This study design improves causal inference by controlling for observable confounding variables, although unmeasured confounders may still bias estimates.

Another study by Dahir and Huyen [126] used hedonic pricing models to examine the impact of proximity to bicycle facilities across 11 U.S. cities between 2000 and 2019. The results were mixed, showing that some types of bicycle infrastructure led to increases in property values, while others had neutral or even negative effects. The direction and magnitude of the impact depended on housing type (single-family vs. multifamily), infrastructure design, and local context. This reinforces the idea that the economic effects of Complete Streets are highly context-dependent and mediated by specific design features.

Other studies have explored related design elements without explicitly referring to Complete Streets. For example, Bowes and Ihlanfeldt [127] found that homes located within 0.5–1 mile of park-and-ride transit stations without parking lots experienced a 1.4% decrease in property prices, whereas Kahn [128] found that walk-and-ride stations increased home values by approximately 3%, while park-and-ride stations had no significant effect.

Overall, although some findings suggest that the economic effects of Complete Streets may be insignificant or mixed in certain contexts, the credibility of such findings depends on the methods used. While many early studies rely on simple before-and-after comparisons or descriptive statistics, more recent work employs propensity score matching, hedonic pricing, or natural experiments to better isolate causal impacts [129,130,131,132,133]. The available evidence suggests that it can have positive impacts on economic development, property values, and employment. In fact, previous research confirms that Complete Streets projects have the potential to increase property values and job growth along the respective corridors, and there is ample evidence from many Complete Street projects across the country supporting these improvements [134].

4.4. Environmental Impacts

Based on the 2008 and 2017 National Household Travel Survey (NHTS), a significant proportion of trips in the United States are three miles or less, with 28 percent being one mile or less. However, many of these short trips are made by automobile due to incomplete streets that make other modes of transportation unsafe or unpleasant. Complete Streets policy has the potential to convert many of these automobile trips into multimodal travel, potentially saving millions of gallons of gasoline each year and improving environmental air quality substantially [10,135]. Despite many studies highlighting the potential role of Complete Streets policy in improving air quality and reducing emissions, the potential environmental impacts of the policy have not been extensively analyzed and quantified in previous literature. Some studies have attempted to measure the environmental impacts of the policy, with mixed findings regarding its impact on air quality and emission reduction. For example, Shu et al. [59] found that a Complete Streets retrofit in Santa Monica, California, improved air quality and increased the number of pedestrians, but did not significantly increase the number of cyclists. In contrast, Peiravian et al. [136] found that vehicle emissions could increase if a project design allows for less space for vehicles, leading to potential congestion. These mixed findings indicate a research gap in this area and the need for further investigation to measure the significance and magnitude of the environmental impacts of Complete Streets policy.

4.5. Health Impacts

Many previous studies and policy guidebooks suggest that Complete Streets policy and other pedestrian-friendly policies can provide an opportunity for individuals to develop a healthier, more active lifestyle by improving access to safer streets in the long term. When streets are transformed into safe, comfortable, and convenient places for people walking, bicycling, riding public transportation, and driving, people of all ages and abilities have more opportunities to be active when they go from place to place or exercise for recreation [137]. Advocates of Complete Streets policy support it for its potential to promote physical activity, prevent obesity, support social equity, improve youth and elderly mobility, reduce automobile dependency and sprawl, preserve open space, and encourage transit-oriented development [138]. The Centers for Disease Control and other public health organizations recommend adopting a Complete Streets policy as an important element in the fight against the obesity epidemic [37,139].

Previous studies have primarily focused on evaluating the impact of Complete Streets policy on health through measuring level of physical activity levels [19,28,49,139,140,141,142]. For instance, Schlossberg et al. [143] found that after implementing a “road diet” in Seattle, Washington, which reduces automobile space and increases bike lanes and pedestrian areas, the number of cyclists increased by 35% between 2007 and 2010. Another study reported that the addition of bike lanes to a busy street in Long Beach, California, nearly doubled the rate of cycling [28].

Brown, Werner [138] assessed the effects of a Complete Streets intervention on physical activity and weight among participants in Salt Lake City, Utah. They found that the use of transit associated with a Complete Streets intervention resulted in beneficial physical activity and BMI outcomes for those who began to use transit, while individuals who stopped using transit gained sedentary activity and BMI and lost MVPA (moderate to vigorous physical activity) minutes. Jensen, Brown [16] used a decision tree technique to examine the relationship between perceived walkability within Complete Streets and active transportation. They found that residents living closer to Complete Streets corridors were more likely to have active transportation trips compared to more distant residents. A review of primarily cross-sectional studies conducted worldwide found that transit use was associated with an increase in physical activity ranging from 8 to 33 min per day. However, only 4 of these studies relied on self-reported physical activity. In the United States, walking to and from transit stations has become increasingly popular, with a 28% rise from 2001 to 2009, according to the National Household Travel Survey. First- and last-mile walking is more common in cities with rail systems, and regular rail riders tend to walk more than other groups, such as drivers or bus riders [138]. Additionally, previous research has shown that transit use increased in areas near Complete Streets projects, as more people were observed at transit stops following the implementation of the policy [71,138]. The overall renovation of the streets resulted in greater pedestrian use, especially in less busy areas prior to the upgrade [16,59].

Although Complete Streets and other pedestrian-friendly policies have many benefits, a few studies have reported opposing findings regarding their true impacts. For example, California’s Complete Streets renovation project did not result in an increase in the number of cyclists but saw a 37% increase in pedestrians [59]. These mixed findings, however, are challenging to interpret because many of the previous studies did not control for the potential shift in transportation practices over time [16]. Therefore, additional research is necessary to better understand these mixed findings and evaluate their various impacts using more advanced methods and additional data.

5. Research Gaps in Policy, Regulation, Implementation, and Evaluation of the Complete Streets Policy Success

The existing literature on Complete Streets primarily focuses on policy and design implications, implementation guidelines, policy objectives, goals, and elements. Some studies emphasize the benefits of Complete Streets, such as safety improvements for all user groups, including auto and transit riders, as well as pedestrians/bicyclists. These studies highlight the strength of the policy content and utilize case examples from various projects across the country to illustrate the state-of-the-practice in Complete Streets implementation [1,33,35]. However, little research has been conducted to confirm and quantify the various benefits of Complete Streets, such as mode shifts towards sustainable modes of transportation, property value increases, economic development, and environmental impacts [66]. Although research on the impacts of transit-oriented and pedestrian-friendly design on travel behavior is extensive, there is limited research specifically focused on modeling travel behavior changes resulting from Complete Streets interventions using travel demand models and other approaches. Future research can potentially address this issue and examine how the comprehensiveness and presence of Complete Streets policy content may relate to transportation outcomes, such as pedestrian or bicycle fatalities, investment in public transit, modal shifts, and vehicle miles traveled.

Additionally, measuring the “completeness” of a Complete Street is essential for policy makers, stakeholders, and city planners. However, most previously developed frameworks for this purpose are insufficient for evaluating Complete Streets projects comprehensively. In addition to transportation and environmental impacts, as discussed in this review, several other impacts should be considered while measuring the completeness of a street. Further work is required to identify and frame performance objectives for different types of streets [39].

Ref. [60] identified a significant gap in Complete Streets programs across the United States in terms of transit. They emphasized the need for guidance and attention from agencies adopting Complete Streets programs to address this issue. The authors discussed how transit vehicles, passengers, and operators were often not listed as part of “all users” in many implemented programs, which highlighted the disparity between the treatment of transit in Complete Streets policies compared with other modes.

Ranahan et al. [35] found that municipalities with active Complete Streets programs were not comprehensively gathering data to measure the impact of their projects. This lack of required data for evaluation and quantification of the various impacts of Complete Streets policy remains a challenge for researchers and policymakers.

While many studies have suggested performance measures such as safety, mobility, delivery, stewardship, and service to evaluate the success of complete street policies, most of these studies focus heavily on motorized transportation. Measures related to the safety and mobility of non-motorized travelers and environmental quality are often overlooked [141]. To address this gap, Sanders et al. [141] proposed a Complete, Green Streets Performance Measure Framework to evaluate pedestrian and bicycle safety and mobility and contribute to evaluating environmental stewardship.

The evaluation and impact analysis of Complete Streets policies face a significant challenge due to a lack of data required for such analyses. As a result, much of the research only focuses on qualitative impacts of individual design aspects, even though the effects of these individual parts can shape the outcomes of the concept as a whole [32]. However, gathering and using appropriate data is necessary to perform more in-depth quantitative performance and impact analyses. To date, little research has directly linked Complete Streets as a package to such outcomes [144]. Instead, researchers have assessed the expected outcomes and benefits of complete street elements individually. This review highlights this gap in the literature and encourages researchers to investigate the effect of the Complete Streets policy through different perspectives.

This review draws on scholarly databases such as Scopus and Web of Science to assess the documented impacts of Complete Streets policy, particularly focusing on transportation behavior, safety, environmental outcomes, and economic benefits. An important limitation in the literature is the limited inclusion of the perspectives of those who directly use and depend on these streets. As the ultimate evaluators and beneficiaries of street design, the general public, especially urban residents, commuters, and those whose livelihoods depend on public space, play a critical role in shaping the perceived success of Complete Streets interventions. However, most existing studies focus on quantifiable metrics such as reduced crash rates or increased retail activity, often omitting experiential and community-level assessments. To address this gap, future research should incorporate community-based evaluation methods such as surveys, participatory design processes, and qualitative assessments of perceived accessibility, safety, and comfort.

Future research should also focus on analyzing the impact of Complete Street interventions on travel behavior and mode choice, which would be important topics for transportation and city planners. The use of smart city technologies in conjunction with urban data analytics techniques can provide valuable data and tools to aid in efforts to close these research gaps [145].

It should be noted that the evidence base for the impacts of Complete Streets is growing; caution is warranted in interpreting results across studies. Variability in reported outcomes may, in part, reflect differences in methodological approaches and how concepts such as context sensitivity are defined and operationalized across studies. This underscores the need for more rigorous and standardized evaluation frameworks.