Traffic Stress Research Articles

Do attitudes and perceptions help to explain cycling infrastructure quality of service?

Many approaches have been developed to assess the performance or Quality of Service (QoS) rendered by cycling infrastructure. The most common methodologies (Level of Service/Level of Traffic Stress) do not consider user inputs. In other disciplines, user perceptions constitute a powerful tool that can help improve and tailor designs. This study was intended to explore the effect of cyclists’ attitudes and perceptions on the perceived QoS of different cycling infrastructures using Structural Equation Modeling (SEM). The SEM model was developed using cyclist surveys applied at 16 locations comprising all typologies of cycling infrastructure in Bogotá, Colombia. We found that user attitudes and perceptions of tangible (e.g., pavement) and intangible attributes (e.g., enjoyment) can explain cyclists’ QoS. The results lead to a better understanding of typical Global South cyclist perceptions when riding, and provide an accurate tool with which to improve cycling infrastructure QoS from a cyclist perspective.

Level of traffic stress-based classification: A clustering approach for Bogotá, Colombia

The Level of Traffic Stress (LTS) is an indicator that quantifies the stress experienced by a cyclist on the segments of a road network. We propose an LTS-based classification with two components: a clustering component and an interpretative component. Our methodology is comprised of four steps: (i) compilation of a set of variables for road segments, (ii) generation of clusters of segments within a subset of the road network, (iii) classification of all segments of the road network into these clusters using a predictive model, and (iv) assignment of an LTS category to each cluster. At the core of the methodology, we couple a classifier (unsupervised clustering algorithm) with a predictive model (multinomial logistic regression) to make our approach scalable to massive data sets. Our methodology is a useful tool for policy-making, as it identifies suitable areas for interventions; and can estimate their impact on the LTS classification, according to probable changes to the input variables (e.g., traffic density). We applied our methodology on the road network of Bogotá, Colombia, a city with a history of implementing innovative policies to promote biking. To classify road segments, we combined government data with open-access repositories using geographic information systems (GIS). Comparing our LTS classification with city reports, we found that the number of bicyclists’ fatal and non-fatal collisions per kilometer is positively correlated with higher LTS. Finally, to support policy making, we developed a web-enabled dashboard to visualize and analyze the LTS classification and its underlying variables.

A cycling-focused accessibility tool to support regional bike network connectivity

Many cities in the United States are working to become more “bike-friendly” through the provision of new bike infrastructure that is safe and attractive for all types of cyclists, from the timid to assured. These efforts are supported by evidence associating low level of traffic stress facilities with increased cycling activity rates and co-benefits related to the economy, environment, and public health. However, not every mile of bike infrastructure provides the same utility, prompting planning agencies with finite financial resources to search for empirical methods to help evaluate what projects will provide the greatest network connectivity benefit and how disparate projects can complement one another to produce a complete bike network. In this study, we introduce the Cyclist Routing Algorithm for Network Connectivity (CRANC), an accessibility-oriented decision-support tool designed to quantify the benefits of new bike facilities for various populations and neighborhoods. Unlike prior tools, this method simulates the route preferences of different cyclist types and trade-offs in travel time and level of traffic stress to model potential changes in destination accessibility that may result from multiple scenarios of citywide and regional bike network expansion. Here, CRANC is applied to the Boston region’s bike network to determine how a proposed shared-use path in Cambridge, Massachusetts will improve accessibility to regional job opportunities and to labor force for employment sites in Cambridge. Our introduced decision-support tool produces unique, meaningful results relevant to a variety of stakeholders, and holds promise as a new resource for transportation researchers and practitioners.

Commuting patterns and bicycle level of traffic stress (LTS): Insights from spatially aggregated data in Franklin County, Ohio

This study analyzes the relationships between bicycle network design and commute mode shares in Franklin County, Ohio. We first adopt the bicycle level of traffic stress (LTS) criteria to measure bicycle network design. Then, we develop a fractional multinomial logit model to simultaneously estimate the determinants of the shares of commuters who regularly go to work by carpooling, riding public transit, bicycling, and walking. The analytical results show that increasing the proportion of low-stress road segments (LTS 2) is statistically significant and positively associated with the share of bicycle commuters at the census block group level. However, we do not observe a significant relationship between the proportion of very low-stress road segments (LTS 1) and the share of bicycle commuters. This study suggests that social and cultural relevant factors are more important predictors of reductions in automobile use as compared to those factors representing road conditions.

Validation of Bicycle Level of Traffic Stress and Perceived Safety for Children

The level of traffic stress (LTS) methodology was developed to measure, track, and improve the suitability of bicycle networks. Thanks to the simplicity of its data needs and interpretation, LTS has been implemented by several states, regions, cities, non-profits, and researchers. However, relatively few validations of the methodology exist. There is a specific gap in relation to safety perceptions for children, an important group since it serves as the critical population for LTS 1. This study validates LTS using a survey of parents in Denver, Colorado, in which they are asked about perceived safety and biking allowance relative to roadway design characteristics. After the LTS score and biking allowance rates for 612 roadway scenarios are determined, a one-way analysis of variance (ANOVA) is used to determine the suitability of LTS for children. Findings suggest that while LTS 1 and LTS 4 align well with stated preferences, parents told that their children would be able to tolerate some roadway conditions—when allowing for adult supervision—that are currently considered LTS 2 or even LTS 3. These scenarios are primarily on low-volume roadways that have bike lanes. By further refining LTS, it is hoped to ensure that all populations have access to safe and comfortable bicycle facilities.

Mapping heat and traffic stress of urban park vegetation based on satellite imagery - A comparison of Bucharest, Romania and Leipzig, Germany

Large and comparatively compact European cities such as Bucharest and Leipzig struggle with considerable urban heat island (UHI) effects characterized by heat and drought together with high concentrations of air pollutants (NO2, SO2, O3, CO2). However, a healthy urban green infrastructure is necessary to reduce the impacts of UHI on human health. Therefore, continuous monitoring schemes are required for green infrastructure in order to improve human life in such cities. Satellite remote sensing can provide the means for monitoring urban vegetation status. In this study, vegetation indices, mostly based on the spectral bands located in the red-edge region, were computed from Sentinel-2 imagery, and land surface temperature (hereafter LST) was estimated from Landsat 8 data. The aim was to assess the individual and cumulative effects of both vicinity to roads and estimated LST on tree vegetation health in urban parks using analysis of variance. Vegetation indices indicated stressed vegetation. However, tracking urban tree health required a combination of indices, and therefore of spectral ranges, rather than one specific index alone, as the effect sizes varied between parks, cities and along the centre-periphery gradient. Therefore, spaceborne data can provide spatially-explicit indicators for stressed urban vegetation and, thus, decreasing ecosystem services delivery. Future studies are encouraged to decipher further the relation the spatial configuration of urban systems and remote sensing based stress indicators of urban trees using publicly available datasets to enable comparative studies.

Establishment and traffic stress response of tall fescue as affected by Mycorrhiza fungi and Trinexapac-ethyl

Heavy traffic regularly causes damage of substantial aboveground parts to turf grasses. Several factors could affect the traffic stress severity, including the number of occasions per season and the soil moisture content during the traffic stress. Mycorrhiza results in numerous advantages to host plant like improving the turfgrass establishment, root structure and also abiotic stress tolerance of plants. Festuca arundinacea remains green during the playing season and it is the most popular turf grass for football. Trinexapacethyl (TE) might be influence the wear as growth retardant. Accordingly, mycorrhiza infection effect on tall fescue establishment, and TE effect on traffic stress after establishment were studied. The treatments, including traffic stress (traffic and non-traffic stress), TE (0 and 200 g 100 m-2) and mycorrhiza (Control; Glomus mosseae and Glomus intraradices) 50 g m-2 were evaluated on two cultivars of tall fescue in two growing season of 2017 and 2018. Both mycorrhizas were significantly colonized on turfgrass root during establishment. G. intraradices inoculation increased the establishment by passing 60 days from seeding in F. arundinacea cv. Barvado. After establishment, traffic stress reduced the relative water content (RWC) in 2017 and 2018, and also reduced the turf quality and soluble sugar content (SSC). TE improved the RWC, SSC, turf quality and also colonization percentage. Mycorrhiza inoculation enhanced tall fescue establishment. TE application at 200 g 100 m-2 had no influence on traffic stress, however, it improved turf quality, RWC, SSC and mycorrhiza colonization.

Cycle accessibility and level of traffic stress: A case study of Toronto

This paper examines the level of traffic stress for cyclists on the street and path network in the City of Toronto. Link as well as intersection stress is calculated to develop a citywide network of cycling stress. The cumulative opportunities reachable at four levels of cycling stress are calculated for each dissemination area in the city. The results show a low level of cycling access (<5000 jobs) across most of the city at low levels of stress (LTS ≤ 2). Only at level of stress three, where cyclists may be required to negotiate with vehicles and may be in proximity of high-speed traffic, does cycling accessibility rise above 15,000 jobs for a sizeable section of the city. The link between low-stress access to jobs and the decision to cycle from home is investigated using a binary logit model. The results indicate that the cycling accessibly measure has a significant effect on choosing cycling as the travel mode with larger effect for low-stress access. The low stress cycling accessibility to subway stations is calculated as an example of the practical applications of this method and illustrates the limited cycling access to many stations in the Toronto network. Further, a theoretical scenario analysis is undertaken comparing different bicycle network scenarios. Three scenarios are tested 1) removing all cycle tracks, 2) upgrading all bike lanes to cycle tracks, and 3) decreasing street speeds by 10 km/h on the road network entire network. Scenario 3 in particular drastically increases cycling access to jobs.

Will parents let their children bike on “low stress” streets? Validating level of traffic stress for biking

Will parents let their children bike on “low stress” streets? Validating level of traffic stress for biking

Bicycle Level of Service for Route Choice—A GIS Evaluation of Four Existing Indicators with Empirical Data

Bicycle Level of Service (BLOS) indicators are used to provide objective ratings of the bicycle suitability (or quality) of links or intersections in transport networks. This article uses empirical bicycle route choice data from 467 university students in Trondheim, Norway to test the applicability of BLOS rating schemes for the estimation of whole-journey route choice. The methods evaluated share a common trait of being applicable for mixed traffic urban environments: Bicycle Compatibility Index (BCI), Bicycle Stress Level (BSL), Sixth Edition Highway Capacity Manual (HCM6), and Level of Traffic Stress (LTS). Routes are generated based on BLOS-weighted networks and the suitability of these routes is determined by finding the percentage overlap with empirical route choices. The results show that BCI provides the best match with empirical route data in all five origin–destination pairs, followed by HCM6. BSL and LTS which are not empirically founded have a lower match rate, although the differences between the four methods are relatively small. By iterating the detour rate that cyclists are assumed to be willing to make, it is found that the best match with modelled BLOS routes is achieved between 15 and 21% additional length. This falls within the range suggested by existing empirical research on willingness to deviate from the shortest path, however, it is uncertain whether the method will deliver the comparable findings in other cycling environments.

Low-stress bicycling connectivity: Assessment of the network build-out in Edmonton, Canada

Studies have shown that a network of safe, connected, and direct facilities can increase urban cycling levels. During summer 2017, the city of Edmonton, Canada, constructed nearly 20 km of protected bicycle lanes on its core neighborhood streets. A rapid and coordinated network implementation was preferred to the more traditional incremental approach to bike lane construction. In this paper, we evaluate the low-stress connectivity improvements afforded by this network build-out. We first classify streets and trails according to the Level of Traffic Stress (LTS) framework, which we adapt to the metric system. Using only LTS 2 and LTS 1 network links, posited to be adequate for most adults, we apply three analyses. First, we draw “bikeshed” maps, which show areas of connectivity around seven central destinations. Our comparison before and after the build-out points to a better integration of the network, with previously separate bikesheds overlapping and allowing uninterrupted low-stress travel to more destinations. This analysis also allows us to identify several central neighborhoods which are disconnected due to remaining high-stress links. Second, we generate roughly three-hundred hypothetical origins located in the central neighborhoods of the city. Reflecting the improved bikeshed integration, we observe a four-fold increase in connected origin-destination pairs. Finally, we find small reductions in trip lengths between connected pairs for some of the trips that were possible before the build-out. However, important detours are still necessary to remain on an exclusively low-stress network when compared to the shortest path using the full network, regardless of LTS. The primary contribution of our research is to develop a method of analysis, based on straightforward tools, to study the city-wide impacts of targeted infrastructure improvements and is most relevant for cities in the initial stages of bicycle network development.

GIS-Based Equity Gap Analysis: Case Study of Baltimore Bike Share Program

As more cities adopt bike share systems, questions regarding equity, accessibility, expansion, and bikability arise. Baltimore City implemented bike share in 2016 with plans to expand it up to 57 stations. This paper introduces a new methodology for an equity-based planning analysis which help minimize segregation and marginalization in planning practices. The proposed geographic methodology incorporates a modified population density-based bike equity index and develops a level of traffic stress index to prioritize bikeshare infrastructure. This study provides a parallel prioritization scheme for implementing bikeshare and supporting cycling infrastructure.

Evaluating OpenStreetMap’s Performance Potential for Level of Traffic Stress Analysis

Increasingly, metropolitan areas are prioritizing growth in the share of trips taken by bicycle to improve health outcomes, transportation affordability, and environmental performance of the transport system. Evidence is building that network quality is an important determinant in bicycle commuting and route choice. One prominent metric of facility attractiveness is bicycle level of traffic stress (LTS). In tandem, OpenStreetMap (OSM) is becoming an important source of network data for routing and for generating measures of multimodal accessibility. Although there are studies that examine the completeness of OSM tags and utilize OSM data to compute LTS on networks, none of them examine the accuracy of these analyses. The goal of this paper is to evaluate the accuracy of OSM-derived LTS predictions and offer quality assurance strategies to reduce inaccurate predictions. This study compares OSM-derived LTS predictions with ground-truthed LTS scores created by Montgomery County. It finds that OSM-derived LTS networks provide comparable results to the ground-truthed data. The OSM-derived LTS scores correctly identified 89.9% of the length of the network as either high (LTS 3 or 4) or low stress (LTS 1 or 2). However, this study demonstrates there is a higher potential for error within certain street typologies and urban contexts, and that low-stress accessibility calculations can be very sensitive to even a small number of incorrectly classified segments. Finally, practices to improve the quality of OSM-derived LTS predictions and low-stress accessibility calculations are suggested.

Implementing Low-Stress Bicycle Routing in National Accessibility Evaluation

The growth of bicycling and bicycle network facilities in the United States warrants assessment of whether bicycle networks give populations safe access to valuable destinations, that is, a bicycle network must be sufficiently both safe and useful. The Bicycle Level of Traffic Stress metric is adapted to assign traffic stress values to street segments and intersections based on OpenStreetMap data, and cumulative job opportunity accessibility calculations are performed on the reduced, low-stress bicycle networks. Four metropolitan areas were analyzed: Minneapolis–St. Paul, MN; Miami, FL; Seattle, WA; and Washington, D.C. An “access gap” metric was proposed, comparing low-stress accessibility with higher-stress accessibility, as a way to gauge how much a city’s bicycle network could be improved through upgrading its higher-stress bicycle facilities. Accessibility was aggregated over a variety of geographic areas, including Core-Based Statistical Areas, municipal boundaries, and neighborhoods, demonstrating the applicability of the proposed analysis framework to a wide variety of scenarios. It was found that, generally, restricting bicycle travel to only low-stress networks results in universal reductions in accessibility, which vary in magnitude between metropolitan areas, and between neighborhoods within a given metropolitan area. Practical applications of a traffic stress-informed bicycle accessibility analysis framework are discussed.

Degradation of piezoelectric device as an energy harvester under equivalent traffic stress condition

Piezoelectric materials have widely been used for applications in microelectromechanical systems, electromechanical devices, civil infrastructure, in transportation and smart devices. The performance of these devices is largely affected by their loading and unloading history when used in electromechanical applications. Lead Zirconium Titanate (PZT), a specific material of piezoelectric ceramics, which upon repetitive cyclic compressive load undergoes both electrical and mechanical degradation over a period of time and number of cycles. The degradation of piezoelectric properties with the application of cyclic compressive loading and the mechanical fatigue behavior were investigated on PZT-5H.

The Keys to Connectivity: The District of Columbia’s Innovative Approach to Unlocking Low-Stress Bicycle Networks

Washington, D.C. (the District) has led the way in the adoption of state-of-the-art bicycle facilities and the innovative application of bicycle level of traffic stress (LTS) mapping for the District. Although the District’s LTS network map provides insight into bicycle network accessibility at the street level, the District needs a data-driven mechanism for identifying and prioritizing future investments to improve cycling at the system level. As part of its ongoing District Mobility Project, District Department of Transportation (DDOT) applied a geographic information system (GIS)-based network analysis to its bicycle LTS map to quantify network connectivity on low-stress District streets. This analysis was used to develop a bicycle network accessibility rating for District neighborhoods. The results revealed that though DDOT has invested in a range of innovative projects to improve accessibility in the District, only 27% of the overall network has been connected. By taking the analysis a step further and identifying the bottom 10% of accessible census blocks, DDOT both confirmed existing perceptions about the presence of disconnected low-stress “islands” in the District, and identified key gaps in the overall bicycle network. Using this information, DDOT is able to prioritize future bicycle infrastructure investments, while possessing a data-driven mechanism for assessing and communicating the accessibility benefits offered by individual investments. In addition, the methodology for developing the network accessibility rating provides a proof-of-concept for other jurisdictions looking to maximize the utility of their own LTS network maps.

An adaption of the level of traffic stress based on evidence from the literature and widely available data

Bicyclist quality of service measures are often difficult to apply on the network rather than facility level. Analyzing bicycle infrastructure on the network level is a critical process for managing bicycle infrastructure planning, design, and construction. The Level of Traffic Stress (LTS) measure fills this need for a network level measure. However, the originally proposed LTS measure leaves some gaps related to the designation of facilities and requires data that may be difficult to collect on a network level. The adapted LTS measure proposed here is based on traffic, roadway, and bikeway characteristics data available to most planning and engineering agencies and on evidence from the literature. The adapted LTS was used to classify and analyze bike network connectivity in two case studies to assess the methodology and demonstrate practical applications in infrastructure management. The first was a six-mile buffer zone of the Atlanta BeltLine Eastside Trail, and the second was a three-mile transit access zone around three transit stations in southwest Atlanta. The analysis was done in ArcGIS and provides results that can be easily interpreted by the public and decision makers, while relying on quantifiable traffic and roadway characteristics.

Fear Factor: Level of Traffic Stress and GPS Assessed Cycling Routes

Background: Cycling currently comprises only 1% of transport trips in the U.S. despite benefits for air pollution, traffic congestion, and improved public health. Methods: Building upon the Level of Traffic Stress (LTS) methodology, we assessed GPS trip data from utilitarian cyclists to understand route preferences and the level of low stress cycling connection between origins and destinations. GPS data were obtained from adult transport cyclists over multiple days. All bikeable road segments in the network were assigned an LTS score. The shortest paths between each origin and destination along bikeable roadways and along low stress (LTS 1 or 2) routes were calculated. Route trajectories were mapped to the LTS network, and the LTS and distances of observed, the shortest and low stress routes were compared. LTS maps and animations were developed to highlight where low stress connections were lacking. Results: There were 1038 unique cycling trips from 87 participants included in the analysis. An exclusively low stress route did not exist for 51% of trips. Low stress routes that were possible were, on average, 74% longer than the shortest possible path and 56% longer than the observed route. Observed routes were longer and lower stress than the shortest possible route. Conclusions: Results indicate that transport cyclists traveled beyond low stress residential areas and that low stress routes with acceptable detour distances were lacking. Cyclists appeared to weigh both route distance and quality and were willing to trade maximum directness for lower stress. GPS data provide additional information to support planning decisions to increase the impact of infrastructure investments on cycling mode share.

Quantifying Bicycle Network Connectivity in Lisbon Using Open Data

Stimulating non-motorized transport has been a key point on sustainable mobility agendas for cities around the world. Lisbon is no exception, as it invests in the implementation of new bike infrastructure. Quantifying the connectivity of such a bicycle network can help evaluate its current state and highlight specific challenges that should be addressed. Therefore, the aim of this study is to develop an exploratory score that allows a quantification of the bicycle network connectivity in Lisbon based on open data. For each part of the city, a score was computed based on how many common destinations (e.g., schools, universities, supermarkets, hospitals) were located within an acceptable biking distance when using only bicycle lanes and roads with low traffic stress for cyclists. Taking a weighted average of these scores resulted in an overall score for the city of Lisbon of only 8.6 out of 100 points. This shows, at a glance, that the city still has a long way to go before achieving their objectives regarding bicycle use in the city.

Measuring low-stress connectivity in terms of bike-accessible jobs and potential bike-to-work trips: A case study evaluating alternative bike route alignments in northern Delaware

When road segments with high traffic stress are excluded, the remaining network of low-stress roads and trails can be fragmented, lacking connections between many origin-destination pairs or requiring onerous detour. Low-stress connectivity is a measure of the degree to which origins (for this study, homes) and destinations (jobs) can be connected using only low-stress links and without excessive detour. Revision 2.0 to Level of Traffic Stress criteria is introduced and applied to the road and trail network of northern Delaware. A propensity model is proposed to reflect people’s declining willingness to ride a bike with greater trip length and detour, accounting for the impact to health and other benefits of cycling. New connectivity measures are introduced that can be interpreted as the number of bike-accessible jobs and the potential number of bike-to-work trips, powerful measures for evaluating alternatives.&#x0D; These connectivity measures are applied in a case study evaluating alternative alignments for a bike route between Wilmington and Newark, Delaware’s two largest cities, separated by a distance of about 20 km through a largely suburban landscape. The case study explores the benefits of enhancing alternatives with branches that help connect to population and employment centers. We also find that the connectivity gain from constructing multiple alignments is greater than the sum of connectivity gains from individual alignments, indicating that complementarity between the alternatives, which are spaced roughly 5 km apart, overshadows any competition between them.