Susan Handy

• University of California, Davis

During the COVID pandemic, at least 97 US cities closed downtown streets to vehicles to create commercial pedestrian streets with the goal of encouraging active travel and economic activity at safe social distances. This study addressed three questions about these programs for businesses located on a pedestrian street: 1) what factors influenced th...

California’s freeways have come under increasing scrutiny for their disproportionately adverse impacts on low-income populations and populations of color. This study uses empirical research to not only understand but also quantify and describe in detail the historical impacts of freeways on communities of color in four California cities and areas:...

This paper examines changes in e-bike awareness and consideration among commuters to the University of California, Davis campus using data from an annual travel survey. The analysis shows that awareness of e-bikes increased among commuters while consideration declined between 2019 and 2021. Awareness significantly increased among staff and undergra...

Bike-share services will produce more limited benefits if users cannot find bikes when and where they need them. Bike-share operators must thus have process for “rebalancing” the bikes within the system to ensure that they are available where demanded. A potentially cost-effective strategy for rebalancing bikes is to offer incentives of some sort t...

Problem, research strategy, and findings Accessory dwelling units (ADUs) are once again a hot topic, as communities across the United States face housing shortages and rising housing costs. For planners and policymakers attempting to facilitate ADU development, it is important to understand the homeowners who do not yet have one. Yet there is remar...

Bike-share service has become popular as a sustainable mode of transport in many cities in the U.S. But growing bike share demand while addressing social equity by providing adequate access to the service to lower-income groups is a challenge for cities. With the goal of informing their efforts, we analyzed the influence of socio-demographic and ot...

A modal shift from car to bicycling could produce broad benefits for transportation efficiency, energy consumption, environmental quality, public health, and quality of life. While major cities in the US have promoted bicycling through a combination of investments in infrastructure and soft programs, bicycling remains at less than 4% of trips acros...

Dock-less e-bike-share use is likely to reduce vehicle miles traveled (VMT) and related greenhouse emissions – if it substitutes for car use. If the major mode shift comes from public transit, owned bike, or walking, the benefits will be more limited. The goal of this paper is to identify the factors influencing mode substitution, defined here as t...

The decline in driver’s licensure among teenagers in the U.S. in recent decades has led some observers to speculate that the newest generation of adults will be less car dependent than those that preceded them. Previous studies have identified a variety factors that may explain the decline, including graduated licensing policies and economic condit...

Local officials in the North America frequently face opposition to new or expanded bicycle or pedestrian facilities. The most vocal opponents are usually motorists and local business owners who fear that the removal of or reductions in vehicular parking or travel lanes will reduce patronage from motorists and that any increased patronage from pedes...

Previous research has demonstrated the relevance of life events to explain changes in travel behavior. Less clear is the moderating role played by life stages on the relationship between life events and travel behavior. Our goal in this study is to explore how the influence of life events on travel behavior differs by life stage. We use data from a...

Ridehailing has become a main-stream mobility option in many cities around the world. Many factors can influence an individual's decision to use ridehailing over other modes, and the growing need of policy makers to make built-environment and regulatory decisions related to ridehailing requires an increased understanding of these. This study develo...

Bike-share services around the US have attracted considerable ridership, although little is known about the factors influencing an individual’s intention to use this service. In this study, we explore the influence of socio-demographics, bicycling frequency, individual latent attitudes towards bicycling and cars, and the social environment variable...

Many existing studies of bike-share services focus on system dynamics and user characteristics, but less is known about how bike share influences individual-level travel behavior and attitudes of residents. While attitudes toward bicycling have a particularly strong association with bicycling behavior, little is known about how bike share influence...

Enjoyment of alternatives to driving can make up for what are often longer travel times in the mode choice calculus. In particular, studies show that liking of bicycling is a significant predictor of bicycling, but few studies have systematically explored what it is about bicycling that people like. We address this question in an exploratory analys...

If we expand roadway capacity, more drivers will come, or so economic theory suggests and a substantial body of empirical research now shows. Despite strong evidence, the “induced travel” effect is often ignored, underestimated, or misestimated in the planning process, particularly in the assessment of the environmental impacts of roadway capacity...

The idea that accessibility is the true goal for transportation planning goes back many decades, starting with notable writings in the 1950s, followed by a flurry of writings in the 1970s. Since then considerable academic work has gone into the development of accessibility measures, but their use in transportation planning is not yet pervasive. In...

PAS report on street connectivity

Understanding how road environments stress bicyclists (and prospective bicyclists) has important implications for road design and network planning. With the rise of wearable bio-sensing technology, the potential for measuring real-time environmental acute stress is emerging. In this naturalistic cross-over field experiment, we investigate bicyclist...

Cities looking to improve environmental, social, and health outcomes from the transportation system consider bicycling an important travel mode now and into the future. One way cities are looking to promote bicycling is by installing public or private bike-share services, where individuals can rent bicycles for one-way trips. Many existing studies...

This paper uses a mobility biography approach to investigate how life course events explain changes in attitudes towards and levels of bicycling. We use 54 interviews conducted with residents of a small US city that include retrospective questions covering six life stages. Three life events emerged from the interviews as influential: parenthood, re...

The availability of ridehailing services, such as those provided by Uber and Lyft in the U.S. market, as well as the share of trips made by these services, are continuously growing. Yet, the factors affecting the frequency of use of these services are not well understood. In this paper, we investigate how the frequency of use of ridehailing varies...

This paper presents a simple method for projecting the impact of new bicycle facilities on vehicle kilometers traveled. Our method starts with existing short-duration bicycle counts on or near the facility corridor, then applies six adjustment factors to project reductions in vehicle kilometers traveled. We examine the feasibility of measuring each...

Efforts to promote non-motorized, active transportation modes typically focus on walking and bicycling. However, other self-propelled devices such as skateboards, roller skates, and push scooters can and are being used as means of transportation. In California, users of these unconventional modes travel up to an estimated 48 million miles per year....

This paper examines the connection between beliefs about modes and liking of modes using data from the annual Campus Travel Survey at the University of California, Davis. The analysis, which focuses on biking and driving, shows that the beliefs about these modes differ significantly but that in both cases the beliefs that the mode is fun and relaxi...

On-demand ride services, such as those offered by Uber and Lyft, are transforming transportation supply and demand in many ways. As the popularity and visibility of Uber/Lyft grow, an understanding of the factors affecting the use of these services becomes more important. In this paper, we investigate the factors affecting the adoption of on-demand...

Many communities have prioritized policy and built environment changes to promote active transportation (AT). However, limited information exists on the partnerships and processes necessary to develop and implement such policy and environmental changes, particularly among organizations in non-health sectors. Within the transportation sector, metrop...

Travel is difficult without the supportive attitudes, norms, and skills that make up “motility,” the capacity for travel. Travel experiences are critical to developing motility. This study identifies factors that influence the development of bicycling motility through analysis of a prospective panel of 19 children, interviewed at ages 9, 12, and 15...

Emerging transportation services are quickly changing the way individuals travel by expanding the set of transportation alternatives available for a trip, allowing for more flexibility in travel schedules and providing access to transportation without incurring the costs of auto ownership. Among the most controversial and rapidly growing shared-mob...

A common method used to evaluate road designs for bicycling is a survey of stated opinions based on imagined bicycling experiences that are used to represent real experiences. However, we know little about the connection between imagined and real bicycling experiences. In this study, we examine the relationship between bicyclists’ (first-person exp...

Although active travel to school for primary school students has been widely studied, research into the determinants of teenage active travel to school is noticeably lacking. Understanding the determinants of teen active travel to school is important given that teenage travel may have implications for the formation of habits that carry over to adul...

Young adults currently obtain driver’s licenses at a substantially lower rate than previous generations. In a handful of recent studies, scholars have evaluated this trend by investigating the association of various factors, primarily personal characteristics and the built environment, with driver’s licensing. However, these studies have examined a...

Studies show that the way an individual feels about bicycling – the degree to which they like bicycling – is an important predictor of whether or not they bicycle. But why do some people like bicycling and others don’t? This study explores factors that may influence an individual’s liking of bicycling, or more formally, their bicycling affect. We a...

Concern about climate change has led to policies in California that aim to decrease greenhouse gas (GHG) emissions from transportation. Although these policies mostly promote technological innovations, some policies aim to reduce GHG emissions by reducing the amount of driving, measured in vehicle miles traveled (VMT), through land use and transpor...

The quality of a worker's commute significantly impacts her well-being. We seek to add to the nascent literature on this topic by examining how travel mode, location, and other personal characteristics are associated with perceived commute quality and then by exploring implications for commute satisfaction. We use data from the annual Campus Travel...

Problem, research strategy, and findings: Big box stores have proliferated across the United States in the last three decades. Proponents have praised them for providing affordability and convenience to consumers, but opponents have criticized them for driving out local businesses, among other negative impacts for communities. We examine the impact...

Transportation agencies’ increased reliance on voter approved financing requires planners to better understand and address voters’ motivations to support ballot initiatives. These initiatives, which can mimic or subvert traditional planning processes, are also opportunities for voters to register backlash against planning initiatives. We examine th...

Background/methods While usually thought of for recreation, skateboards can and are used for travel. Recreational skateboarding, an “extreme sport”, can carry a reputation for danger. What is the safety performance of skateboard travel? This study explores skateboard travel safety by (1) examining fatality and injury data, and (2) observing how ska...

Attitudes are thought to play an important role in determining people’s travel behavior, although researchers have acknowledged the possibility of a reverse relationship. Given the importance of knowledge about the direction of causation as a basis for policies and programs designed to effect behavioral change, the scarcity of in-depth research on...

The growth of online shopping will likely impact rates of in-store shopping, signaling potentially significant ramifications for shopping-related vehicle travel. To better understand this relationship, we studied shoppers in Davis, California using a comprehensive survey dataset to explore the effect of personal characteristics, attitudes, percepti...

Several studies have rigorously documented the induced travel effect, in which added highway capacity leads to added vehicle travel. Despite the evidence, transportation planning practice does not fully account for this phenomenon, with the result that estimates of the potential congestionreducing benefits of added highway capacity may be overstate...

Fare evasion is a problem in many public transport systems around the world. Policies to reduce this problem are generally aimed at improving control systems and increasing fines for offenders. In this paper, we attempt to identify the joint impact of different variables explaining fare evasion using an econometric study. The variables found to be...

This study explores bicyclist behavior in San Francisco using data collected before and after major bike infrastructure investments. From early 2011 to December 2013, investments of $3.3 million correlated with a 14% increase in counts of bicyclists, part of a 96% increase in bicyclist counts from 2006 to 2013 (San Francisco Municipal Transportatio...

Context: As obesity has become increasingly widespread, scientists seek better ways to assess and modify built and social environments to positively impact health. The applicable methods and concepts draw on multiple disciplines and require collaboration and cross-learning. This paper describes the results of an expert team׳s analysis of how key d...

With the goal to improve the integration of multiple travel modes into traditional roadway designs, many jurisdictions have considered road diets, characterized by reductions in vehicular traffic lanes and reallocation of right-of-way for other modes. Studies show that road diets can improve safety without slowing automobile traffic, but benefits f...

The decline in active travel to school and the concomitant rise in numbers of children being driven to school in the United States over recent decades have affected the health of school-age children and contributed to environmental problems. In response, communities throughout the country are stepping up efforts to increase active travel, including...

Growth in online shopping market share will likely lead to changes in consumer travel patterns. In response to the inevitable transportation impacts of online shopping, a detailed exploratory analysis of shopping survey data (excluding food purchases) was conducted with Davis, California, as a case study. Davis was notable for its lack of major big...

Trends in decreased car use and car-licensing rates have been observed in several industrialized countries in the past decade. This study assessed whether and to what extent this decline may (partially) be attributed to the latest trends in the digitalization of society, in particular the growing use of mobile Internet devices (smartphones and tabl...

Given the potential benefits of bicycling to the environment, the economy, and public health, many U.S. cities have set ambitious goals for increasing the bicycle share of commute trips. The Transtheoretical Model of Behavior Change, which seeks to describe how positive and permanent change can be fostered in individuals, may shed light on how citi...

Growing concerns about climate change and traffic congestion are motivating policymakers to find ways to encourage sustainable travel options. In the United States, where 88 percent of shopping trips are made by car, research identifying the factors that influence shopping mode choice can provide insight into ways to divert some of these trips to m...

Background A growing body of evidence shows that youth who walk or bike to school have higher levels of overall physical activity. In turn, greater physical activity is associated with lower incidence of chronic disease and better physical and psychological wellbeing. This association is especially important considering the increasing prevalence of...

This paper introduces a set of articles about how transportation planners need better tools for estimating trip generation, and to develop better tools we need more data collection, especially methods that capture passenger trips by personal vehicles, transit, walking, and bicycling, as well as freight trips. With such data in hand, researchers wou...

Many cities are encouraging bicycling as mode of transportation as a way to improve air quality and health. Evidence suggests a strong influence of attitudes on bicycling, but few studies have examined the formation of attitudes toward bicycling. This paper explores the potential effect of crashes and other incidents on attitudes towards bicycling....

This paper describes a practical method of adjusting existing Institute of Transportation Engineers (ITE) estimates to produce more accurate estimates of motor-vehicle trip-generation at developments in smartgrowth areas. Two linear regression equations, one for an A.M. peak-hour adjustment and one for a P.M. peak-hour adjustment, were developed us...

In recent years the number of teenagers and young adults acquiring a driver's license has declined in many developed countries worldwide, with long-term implications for transportation planning. However, the reasons for this decline are only partially understood. Some research has focused on surveys of young drivers without licenses, but few studie...

Many cities and states rely on aggregate seal coats (chip seals) to main- tain roads. Chip seals are economical as a surface for lower-volume roads or for preservation treatments on asphalt roads, and the technol- ogy for increasing the life span of chip seals is continually improving. Chip seals often have higher macrotexture than do asphalt or co...

The role of bicyclists as consumers is explored through an examination of the relationship between travel mode and shopping behavior. As cities develop policies to combat congestion and reduce emissions from the transportation sector, tension often develops when scarce road space must be allocated, particularly in dense urban cores. The challenge i...

Land-use policies are frequently proposed as a means of reducing the negative impacts of transport on the environment, such as emissions of CO2 and pollutants, and noise nuisance. In this paper we discuss whether land-use policies make sense as a strategy for reducing vehicle travel and lessening environmental impacts. We conclude that they do, but...

Researchers in the transportation field rely heavily on traditional random-digit-dialing phone surveys and increasingly on online surveys. Many studies have looked at the strengths and weaknesses of the two methods, but few have examined differences in the inferences that can be drawn from the data generated by the two survey methods. In this paper...

Awareness of the many different connections between health and travel is growing. While safety has long been the pre-eminent health concern in the transportation field, the health impacts of harmful pollutants became a public concern starting in the 1950s, and concerns over a decline in active forms of travel rose to prominence in the last decade....

The environmental benefits of bicycling and walking depend on the degree to which their use substitutes for car driving. Assuming that every walking and bicycling trip replaces a driving trip is likely to produce overestimates of the potential for such modes to reduce vehicle travel and city-scale greenhouse gas emissions. Measuring this “substitut...

In some parts of the world, electric bicycles (e-bikes) represent a significant share of daily travel, though they are still rare in the United States. The small size and maneuverability of e-bikes that are assets in cities in China may not be as important in the U.S., where cities are built to accommodate cars, but their potential as a substitute...

Cycling as a mode of transportation has many advantages for both cyclists and society: it is a low-cost, low-polluting, health-improving way to travel. In light of these benefits, a growing number of cities throughout the world are implementing policies to promote cycling, though they continue to struggle to identify the most effective ways to spen...

Land-use policies are argued by both researchers and policy makers to be a strategy for reducing negative impacts on the environment through reduced motorized-vehicle travel. But does research support this argument? In this context we discuss whether land-use policies make sense as a strategy for reducing motorized travel and lessening environmenta...

This study presents a method to quantify multimodal trip generation for developments in smart-growth areas. The technique combines door counts and intercept surveys to classify trips by mode, and it has several advantages over existing methods that use automated technologies to count automobiles entering and exiting access points to developments. T...

This study aims to establish whether or not bicycle commuting and cycling for other purposes (e.g. shopping, visiting friends) are related over time. Using previously gathered panel data (the Dutch mobility panel) these relationships are revealed by (1) a series of conditional change models and (2) a latent transition model. The conditional change...

Concerns over climate change have brought new impetus to the goal of reducing vehicle travel through land-use policy. To determine the degree to which land-use policies are effective in reducing vehicle travel, studies are needed that measure and compare vehicle travel both before and after a land-use policy change. The opening of the first big-box...

The environmental, economic, and health benefits of bicycling provide motivation for policy makers to promote bicycling as a means of transportation. Research has linked sociodemographic factors, individual attitudes, and characteristics of the social and physical environments to the decision to bicycle. A study was conducted to identify and estima...

This paper explores measures of pedestrian accessibility and network connectivity with a network that includes pedestrian facilities in addition to the street network. Studies that focus on walkability usually use available street networks that do not include pedestrian-only facilities. The effect of missing pedestrian connections where the street...

It is well known that a standard application of the ITE trip rates for an area with many smart growth characteristics will result in an over-estimation of the number of trips generated. No commonly agreed on methodology in the United States for estimating trip generation takes into account the smart growth characteristics of a land use development...

Between 2003 and 2008, a total of 25 partnerships funded through the Active Living by Design (ALbD) program worked to change built environments and policies in communities to help citizens be active in their daily routines. This paper systematically summarized the scope of ALbD physical projects and policy changes, described resources generated by...

In this paper, we present a discussion of the challenges for research on the topic of vehicle miles traveled. We then summarize and critique evidence from the US on the association between 14 distinct factors and vehicle miles traveled. Our results quantify how much vehicle miles traveled can be expected to change in response to changes in policy o...

Rates of walking and bicycling to school in the US have been declining for decades, with implications for public health and the environment. Planners and policy makers are looking for ways to reverse the trend through such programs as Safe Routes to School. However, the research on school travel mirrors the policies in leaving important gaps: most...

Working at home is widely viewed as a useful travel-reduction strategy, and it is partly for that reason that considerable research related to telecommuting and home-based work has been conducted in the last two decades. This study examines the effect of residential neighborhood built environment (BE) factors on working at home. After systematicall...

In light of the increasing reliance on compact growth as a fundamental strategy for reducing vehicle emissions, it is important to better understand how land use-transportation interactions influence the production of mobile source emissions. To date, research findings have produced mixed conclusions as to whether compact development as a strategy...

Many studies have found cross-sectional associations between characteristics of the neighborhood built environment and physical activity (PA) behavior. However, most are based on self-reported PA, which is known to result in overestimation of PA and differential misclassification by demographic and biological characteristics. Cardiorespiratory fitn...

We examine the role of social networks in enabling access to private-vehicle transportation, through getting rides and borrowing cars. Based on qualitative findings from ten focus group discussions with recent Mexican immigrants to California, half of whom have no car, we describe the extent to which participants depend on rides and borrowed cars f...