While the installation of lower-stress bicycle facilities has been linked with greater increases in bicycle commuting, the extent to which facilities' effectiveness is influenced by broader bicycle network characteristics remains unclear. To what degree does bicycle network density amplify the effect of bicycle facilities on bicycle commuting? Using multiple linear regression models and elasticity analyses, this study examined the interplay between bicycle facility installation and bicycle network density and their influence on bicycle commuting in 14,011 block groups across 28 U.S. cities. Findings suggest that bicycle network density exhibited stronger associations with ridership growth than the installation of individual facilities, with network effects exceeding facility installation effects by a factor of 4.6. More specifically, the installation of protected and buffered bicycle lanes was consistently and significantly associated with increased bicycle commuting, but the installation of standard bicycle lanes lost significance after the presence of a wider bicycle network was accounted for (the installation of shared-lane markings and off-road trails demonstrated non-significant relationships with bicycle commuter changes). Protected bicycle lane installations also produced meaningful ridership gains even in lower-density bicycle network contexts (elasticity of 0.48) with diminishing returns as bicycle network density increased (elasticity of 0.24). In contrast, higher-stress facilities demonstrated higher elasticities when moving from medium to high network density (elasticity of 0.57), indicating that their effectiveness is more dependent on a well-connected bicycle network. Taken together, these findings highlight the importance of prioritizing not only high-quality, low-stress bicycle facilities but also the development of continuous and connected low-stress networks.

Purpose Past urban transportation safety efforts have largely focused on controlling road user behavior through tactics such as speed management and separating users in space and time. This research moves beyond roadway behavior to examine associations between kinetic energy exposure and safety via travel behavior factors such as vehicle miles traveled (VMT) and mode share. Design/methodology/approach After analyzing 227 USA urban areas and controlling for state-level heterogeneity via linear mixed-effects models, we found that kinetic energy exposure is more strongly associated with transportation safety outcomes than variables focused on roadway behavior such as vehicle speeds, education requirements, enforcement efforts, alcohol involvement or seat belt use. Findings Urban areas with lower commute mode share by car and, to a lesser extent, lower VMT are most strongly associated with lower per capita transportation fatality rates. Originality/value These results add new knowledge by suggesting that, in addition to focusing on trying to get people to behave better on the roads – as many current safety frameworks do – reducing driving exposure by facilitating shorter driving distances and providing viable multimodal options is also strongly associated with improved safety outcomes. The findings suggest that prevailing transportation safety paradigms, such as the Safe System Approach, may benefit from greater consideration of driving exposure.

As cities work to develop safer, more connected multimodal transportation networks, prioritizing bicyclist safety has become increasingly critical. Transportation agencies traditionally focus their bicycling safety resources on corridors with high crash numbers. However, this method may overlook streets with fewer crashes but higher risk per bicyclist. Exposure-based safety metrics consider the relative level of bicycling and might offer a more comprehensive understanding of safety. Although standard practice for vehicle road safety work, few cities collect the bicyclist count data needed for similar assessments. This research compared the safety of two corridors: one identified by a hot-spot analysis with a high number of bicyclist-vehicle crashes; and a major arterial in the city's High Injury Network (HIN), but one that is seemingly safer for bicyclists given the relative scarcity of bicyclist-vehicle crashes. Findings suggest that the HIN corridor, despite fewer bicyclist-vehicle crashes, presented a significantly higher relative risk to bicyclists-when accounting for bicyclist exposure-than the corridor identified via hot-spot analysis. We then examined routes parallel to the HIN corridor to gauge whether bicyclists were avoiding such streets and if collecting additional exposure data on the adjacent streets further enhanced our understanding of safety. Results suggest that bicyclists were avoiding the HIN corridor and that it may be more dangerous than crash-count-focused analyses would reveal. This research underscores the importance of expanding data collection efforts to include exposure metrics for bicyclists, to enhance safety evaluations, guide infrastructural improvements, and support public health by promoting safer, active transportation.

BACKGROUND:This study extends beyond traditional speed and conflict management approaches to explore the role of kinetic energy exposure in shaping road safety outcomes. METHODS:We examined the associations between exposure-based metrics (ie, mode share, vehicle miles travelled (VMT) and commute time) and fatality rates (ie, overall, vehicle occupant, pedestrian and bicyclist) by analysing 227 urban areas across 45 US states, controlling for other transportation and socioeconomic covariates. We used linear mixed-effects models to account for unobserved heterogeneity at the state level. RESULTS:The results indicate that exposure plays a central role in shaping traffic fatality rates. Overall, measures of auto-dominance - particularly automobile mode share and VMT - are most strongly associated with higher fatality rates. When examining specific road users, time spent in the transport system emerges as a key predictor across modes. However, mode share appears more strongly associated with safety outcomes for vulnerable road users (ie, pedestrians and cyclists) whereas VMT is more strongly associated with motor vehicle occupant fatality rates. Notably, exposure-related factors remain strong and significant even for individuals travelling in cars, underscoring that increased system exposure elevates risk across all user types. DISCUSSION AND CONCLUSIONS:Our findings also reinforce the association between socioeconomic and demographic conditions and safety outcomes. However, in addition to longstanding strategies focused on kinetic energy severity (eg, speed management) and kinetic energy likelihood (eg, conflict management), our results suggest that reducing fatality rates requires reducing overall kinetic energy exposure. Providing viable modal alternatives and designing communities that enable shorter travel distances and less time spent in the transportation system may be critical components of a comprehensive road safety strategy.

Existing research links standard bicycle lanes with increased levels of bicyclist commuting. Here we question how newer facility types fare relative to standard bicycle lanes. Using 6 years of longitudinal data across 14,011 block groups in 28 US cities, we find that block groups that installed protected bicycle lanes experienced bicycle commuter increases 1.8 times larger than standard bicycle lane block groups, 1.6 times larger than shared-lane marking block groups and 4.3 times larger than block groups that did not install bicycle facilities. Focusing on mileage, protected bicycle lane mileage installed was significantly associated with bicycle commuter increases 52.5% stronger than standard bicycle lane mileage and 281.2% stronger than shared-lane marking mileage. The results suggest that lower-stress bicycle facilities—such as protected bicycle lanes—are significantly associated with larger increases in ridership at the block-group level compared with higher-stress facilities such as standard bicycle lanes and shared-lane markings.

Transportation access significantly impacts inclusion, well-being, and health. However, people with disabilities often struggle to use fixed-route transit due to mobility challenges. The Americans with Disabilities Act (ADA) mandates complementary paratransit services, but these services remain inefficient and unreliable.This study analyzes 1.16 million paratransit trips in the Denver region, comparing travel time reliability with car travel times using FHWA’s reliability indices: the Planning Index, Buffer Index, and Misery Index. We normalized the data using the paratransit user trip rate (PUTR), a ratio of trip distance to trip time, and conducted user interviews to provide insights into lived experiences and perceptions of service quality.The results suggest significantly lower travel efficiency compared to car travel, with paratransit users experiencing much longer and less predictable trips. More specifically, paratransit trip times are highly volatile, requiring riders to plan for worst-case scenarios to ensure on-time arrival 95% of the time. On average, paratransit users must allocate 3 hours for trips that would take 20–30 minutes by car. The unpredictability of travel forces riders to overbudget time, significantly impacting daily mobility and quality of life.

A common perception is that the transportation experiences of people with disabilities have improved dramatically since the passing of the Americans with Disabilities Act (ADA) in 1990. Though much progress has been made, many aspects of the current transportation system still limit people with disabilities from traveling safely and efficiently. Moreover, transportation planning and design efforts consistently lack representation of people with disabilities. This research seeks to address this disconnect via semi-structured interviews with (i) 28 stakeholders who self-identify as having a disability; and (ii) 9 government officials whose work intersects with the supply of infrastructure regulated under the ADA. All interviewees reside or work in the Denver region in Colorado. One objective is to understand how attributes of transportation infrastructure affect the daily mobility of people with disabilities. A second is to comprehend how the programming and management of transportation assets affects navigation for people with disabilities. Through a thematic and content analysis of the interview corpus, we reveal the challenges faced by people with disabilities through hard infrastructure issues and the programming or management of transportation facilities. Together, these act to diminish the quality of mobility options for people with disabilities. When working to create a transportation network that is universally accessible, it is critical for planners and engineers to work with people with disabilities when considering the design needs of individuals with different types of disabilities.

Problem, research strategy, and findingsThe Americans with Disabilities Act (ADA), passed in 1990, set requirements that public agencies in the United States, which receive federal funds, must remove physical barriers in the public right-of-way that might prevent someone with a disability from accessing goods and services. ADA's impact on transportation extends from equitable access in public transportation to meeting compliance requirements for curb ramps at intersections. Researchers argue that public agencies are still falling behind in ADA implementation due to scarce funding, inadequate asset inventory development, and limited transition/compliance plans. We asked: What can organizations and practitioners do to improve ADA implementation for infrastructure design and supply? We relied on an online survey (n = 206) and semistructured interviews (n = 36) with transportation practitioners across the United States. The findings revealed that ADA implementation has been thwarted due to three primary themes that make meeting ADA implementation in transportation challenging: 1) political priorities and organizational coordination that limit ADA in practice; 2) limited guidance, resources, and capacity; and 3) challenges with retrofits, new construction, and maintenance.Takeaways for practiceOur work suggests that organizations and practitioners wish to expand ADA implementation, but to achieve this, additional monetary resources and employee training are needed. Requiring ADA asset inventories and compliance plans, along with developing a framework to improve accessibility from project conception to postdelivery, could incentivize widespread ADA implementation.

Cities with high levels of bicycling tend to be some of the safest cities for all road users. This paper investigates why this relationship exists for fourteen small and mid-sized cities across the U.S. (seven with high bicycling rates and seven paired comparison cities) using ten years of data and hierarchical negative binomial regression models. Findings confirm that higher-bicycling cities are significantly associated with better overall road safety outcomes. In terms of mode choice differences, pedestrian ‘safety in numbers’ as well as reduced driving activity had a positive impact on pedestrian safety. Results from hierarchical negative binomial regressions also suggest that more compact cities were significantly associated with better road safety outcomes for all road users. In terms of socio-demographic and socio-economic factors, the results reveal equity concerns with areas with lower incomes and more non-White residents seeing more overall road fatalities.

Many rigorous studies have shown the effectiveness of helmet use in reducing severe injuries and fatalities to motorcyclists. NHTSA reports estimates of lives saved by U.S. motorcyclists wearing or potentially wearing helmets. This calculation uses a statistically derived estimate of helmet effectiveness in preventing deaths to motorcyclists involved in crashes. Two parts of the estimate of lives saved are (a) deaths prevented assuming crashes occurred that did not kill helmeted motorcyclists in proportion to those that did kill helmeted motorcyclists and (b) deaths that may have been prevented if unhelmeted motorcyclists killed in crashes had been helmeted. Similar estimates can be made for injuries. More readily available crash data enable analysts to investigate whether crashes in their jurisdictions support the inherent assumptions of these estimates. Moreover, the estimates can be stratified to include other crash characteristics such as crash type and rider gender and age. This study compared estimates of potential fatality and injury reductions based on NHTSA averages with estimates with the use of all reported crashes on Colorado state and federal roads in the years 2006 to 2014. Helmet effectiveness is found to depend on crash characteristics in Colorado and does vary from national averages.

The Americans with Disabilities Act (ADA) stipulates that paratransit mobility be comparable to public transit. However, with just under 5% of the population relying on public transportation, transit is not a representative benchmark. To highlight this inequality, we compare trip times by paratransit to counterfactual car-based travel. Using 2.5 years of demand data from the Denver Regional Transportation District’s Access-a-Ride service, we compare paratransit trip times to counterfactual car-based trips for the same origin–destination pairs, controlling for various trip characteristics. Compared to car travel, the findings indicate high variability and uncertainty associated with paratransit trip times. For the same origin–destination pairs, the mean paratransit trip time is almost twice that of the mean car travel time, with a standard deviation for paratransit trip time fourfold that of the standard deviation for car trip time. For perspective, traveling an average of 10 mi during the 7–8 a.m. morning peak can take about 16 min by car with almost no variability, while that same trip can take an average of 25 min by paratransit, with 5% of trips being outside the 95% confidence interval and thus unpredictable. Paratransit trip time inefficiency tends to be particularly worse for females; older adults; those making trips between 9 and 11 a.m.; cash-paying customers; those making shorter trips; and those traveling during inclement weather, including cold temperatures. These findings suggest a need to re-assess using public transit as a benchmark for paratransit supply as regulated by the ADA.

The process of driving cessation typically begins when individuals lose the physical and cognitive abilities to safely operate a car as they age, eventually ceasing to drive entirely. But driving cessation can also occur at any age as a result of injuries or disabilities. Regardless of one's age, losing the ability to drive safely has serious implications for road safety and access to vital services. This research explores attitudes around driving, aging, and driving cessation. We identify correlations between personal characteristics, the place in which one lives, and one's attitudes with the desire to continue driving throughout one's life. We do so using survey data from a mail survey conducted in the Midwestern US joined with built environment characteristics for analysis. We first identify four attitudinal factors using principal components analysis: auto-dependent lifestyle, reducing auto -dependence, auto-as-identity, and reluctant auto-dependence (i.e., reliant on a car for transport, despite a desire to the contrary). We then demonstrate through stepwise linear regression that the desire to continue driving as one ages is significantly correlated with pro-car attitudes, youth, and residential density. Alternately, reluctant auto-dependence and increasing age are associated with reduced desires to continue driving as one ages. Attitudes - both pro-car and anti-car-dependence - explain the majority of the variance in the outcome. This work suggests that policy-makers may find popular support across generations to address driving cessation, and in so doing, address auto-dependence for all of society.

This article investigates factors associated with fatal and severe injury pedestrian crash percentages at intersections in Colorado. Many published studies associate road and traveler characteristics with the frequency or severity of pedestrian crashes without reference to specific locations. The objective of this study is to determine whether road and traveler characteristics, aggregated by intersection, partly explain differences in severe crash percentages at intersections. From 2006 to 2018, there were a total of 17,047 reported crashes involving pedestrians and motor vehicles in all of Colorado. This study analyzes 3,015 of these crashes that had the GPS coordinates needed to identify their locations at intersections and included the information needed to identify the pedestrian outcomes of the crash. The results of logistic and linear regressions found that lighting condition, vehicle speed, turning movement of vehicle, vehicle type, pedestrian age, and driver or pedestrian impairment by drugs or alcohol were most associated with severe crash percentages at intersections. These findings identify crash characteristics at intersections with higher severe crash proportions that can potentially be addressed to improve safety.

Lower-income areas experience an increased incidence of traffic crashes, injuries, and deaths than more affluent ones. Researchers tend to blame these outcomes on differences in car ownership, with lower-income households expected to use vulnerable active modes at higher rates, as well as being more likely to drive older vehicles with fewer safety features. While these explanations seem plausible enough, they likely fail to provide a complete picture of the problem. This study examines the role of the built environment in road safety outcomes for lower- and higher-income block groups in Orange County, Florida. It finds that the hazard posed by urban arterials is three times greater for lower-income environments than for more affluent communities. Sidewalk buffers, ordinarily regarded as a pedestrian amenity, were associated with crash increases in affluent areas but not lower-income ones. Areas with concentrations of black residents were found to be increased risk, even after accounting for differences in income. Considered as a whole, the risk factors for lower-income and high-income populations are not the same. This article examines the underlying reasons that lead to these outcomes and discusses the need to better account for the manner in which design may uniquely affect the safety of different demographic cohorts.

America's "crumbling roads" currently headline the infrastructure zeitgeist, but deteriorating sidewalks are also in desperate need. Sidewalks can be vibrant, social conduits in cities that, when safe and well-maintained, enhance public health and enable accessible passage for all residents, particularly the most vulnerable. The scant but burgeoning research on pedestrian infrastructure has largely focused on data collection technologies and spatial analysis. This research instead seeks to uncover the similarities and differences in how American cities treat their road versus sidewalk networks by asking: are these two indispensable assets of daily urban public life repaired, maintained, and funded disparately? The research was structured around interviews with employees of 16 U.S. cities about their road and sidewalk policies and procedures. We found multiple disparities between roads and sidewalks in and among American cities, including: municipality responsibility, repair timeliness, data availability, and condition assessment. We also discuss cities' pressing concerns for these assets and directions for future research. The implications of this study could affect several themes across transportation infrastructure, including project prioritization, equity, and efficient government spending.

Data on sidewalks have long been deficient. But advances in remote sensing are beginning to increase data prevalence and accuracy. These sidewalk datasets rarely, if ever, account for static obstructions in the sidewalk such as signs, street furniture, or trees. This paper seeks to determine how much of a difference accounting for static obstructions will make when measuring the clear width of sidewalks. We extracted the minimum width of sidewalk surfaces-both with and without accounting for static obstructions-for the entirety of Cambridge, MA, using new GIS methods described in this paper. We then compared these results against Americans with Disabilities Act (ADA) standards for clear width as well as national and federal sidewalk guidelines. The results suggest a significant decrease in the average clear width of sidewalks when accounting for static obstructions. More specifically, the clear width of the average sidewalk drops from 4.5 ft (1.4 m) to 3.5 ft (1.1 m). The percentage of sidewalk segments meeting the 3-ft ADA standard drops from 78% to 51% when accounting for static obstructions. For the proposed 4-ft (1.2-m) ADA standard, it plunges from 59% of sidewalk segments meeting the width threshold to 31%. These results demonstrate that not accounting for static obstructions could lead to a gross overestimation of seemingly adequate sidewalks and an unrealistic assessment of sidewalk infrastructure and pedestrian accessibility.

This study investigates the feasibility of utilizing high-density mobile Light Detection and Ranging (LiDAR) to measure urban streetscape features. The results suggest that mobile LiDAR’s density allows for much smaller voxels than in the previous research and the ability to measure small urban streetscape features in 3D. This includes street trees, light/lampposts, street furniture, traffic and commercial signage, building window proportions, awnings, and enclosed courtyard restaurants. Moreover, mobile LiDAR facilitated measuring and categorizing these streetscape features in walkable, downtown-like streetscape environments. The ability to compartmentalize such streetscapes into smaller cubic foot voxels to be quantitatively measured and categorized could supplement or replace conventional audit-based streetscape measurement. This study introduces new methods—based on voxel data analysis—to compile accurate descriptive statistics of streetscape features and how they can be represented in 3D.

How well has the recent expansion of bicycling networks advanced transportation justice through appropriate distribution across the socioeconomic/demographic (SED) spectrum? Furthermore, does the installation of bicycling facilities lead to SED changes in a neighborhood or vice versa? We longitudinally assess 11,010 miles of bicycling facilities over ten years (2010-2019) in 11,293 block groups across 29 U.S. cities by facility type. Findings suggest inequalities in bicycling facility installation with People of Color (POC) experiencing the lowest rates of overall facility installation. However, bike lane installation was concentrated in lower-income areas (both POC and White). The causality relationships between bicycling facilities and SED changes were weak and largely non-significant. Income increases were followed by bicycling facility installations more so than increases in White populations were followed by bicycling facility installations. SED changes were more correlated with later bicycling facility installation than the inverse, suggesting that bicycling facilities were not linked to displacement.

“Green Projects to Pavements” A Project-Based Learning Approach to Introducing Sustainability to Civil Engineering StudentsMost individuals from birth on learn in an inductive manner (ie. learning from discoveryor observation, contrary to most styles of teaching used in the classroom today. Today’seducation system adheres to a deductive style in which instructors present thefundamentals that lead to application. In addition, the majority of engineering studentsare visual, sensing, and active learners where as, traditional delivery in engineeringacademia is auditory, passive, and sequential. This incompatibility in learning styles anddelivery methods may result in some students’ lack of interest in the course, decreasedperformance, and potentially a decrease in student retention. The objective of this studywas to evaluate the problem-based learning approach in introducing sustainability andconcrete design and placement in an effort to increase student learning. The goal of anyinstructor is to engage students and find more effective methods of teaching coursetopics. This study addresses these objectives and provides faculty teaching similarcourses at other institutions the necessary information needed to implement this program.Sustainability is a major topic that is being addressed by city, state, and nationalgovernments as well as globally. It is important for students to be introduced tosustainability as they will be the individuals forced to consider resource consumption,greenhouse gas emissions, and heat island effect. This Green Projects-to-Pavements program introduces the topic of sustainabilitywhile enhancing materials learning through a project-based learning approach. Thisprogram was implemented in the junior level civil engineering course Introduction toStructural Materials at the University of Colorado Denver. Students were provided aproject goal (design, test, and place a sustainable concrete pavement) and given access toresources that aided in their design of a sustainable concrete mixture. The instructoracted as a facilitator and advisor to the students as opposed to the instructor using adeductive approach and lecturing on the topic. This program introduces a learning stylethat is more compatible with typical engineering students (inductive, active, and sensory(visual and kinesthetic styles). Students were active in performing their own researchrather than being passive listeners in course lectures. In addition, the students mixed andtested concrete themselves which provided for a more “hands on” role in the learningprocess. Students experienced both visual and kinesthetic learning through seeing theconcrete mixed and tested as well as physically placing the concrete during theapplication phase of the study The performance of the students using this teaching style was assessed using twomethods. First, assessment was performed by comparing exam questions related tosustainability and design of concrete with previous course offerings. In addition, theproject final reports submitted by the students were reviewed by both the instructor aswell as industry professionals to assess the quality of the reports.