Pedestrian Comfort Research Articles

A micro-scale look into pedestrian thermophysiological comfort in an urban environment

Different spatial scales enable the analysis of thermophysiological conditions of pedestrians in an urban environment. A higher resolution hotspot analysis was conceived using GIS technology in some areas of Lisbon with different morphological conditions. Eleven hotspots were found across six study areas, located in high to moderate urban density conditions and in different types of urban spaces. So, six hotspots were found in avenues (high urban density conditions), three in streets, and two in general open spaces (moderate urban density conditions). These spaces are characterized by being busy areas with high anthropogenic influence, with high-absorbing and reflective materials, and with very poor green infrastructure. Environmental conditions, namely, radiation, mean radiant temperature, and air temperature, were the main cause of hotspot existence, and the main propellers for UTCI intensification. The urban density variable was also found to be important, especially in avenues and open spaces. In these areas, the adjusted component for environmental and urban density conditions can increase 0.60 to 1.35 °C in open spaces and 0.30 to 0.60 °C in avenues, each time there is a one-unit increase in the component. Trees, either in the street or in parks, have generally been found to decrease the UTCI.

Evaluation of pedestrian thermal comfort from a whole-trip perspective: An outdoor empirical study

Pedestrian thermal comfort is a critical factor influencing urban livability and sustainability. However, existing models often overlook its cumulative impact from dynamic thermal experiences throughout the whole-trip. This study builds on previous findings, conducting outdoor mobile observations in Guangzhou's urban blocks on clear summer days. Methods for assessing thermal comfort during pedestrian travel were tested and refined, taking into account participants' skin temperatures and accumulated heat storage. The research found that the dynamic changes and non-uniform distribution of radiant temperature are the main characteristics of pedestrians' thermal experiences during summer clear weather and are critical factors affecting their thermal comfort. Non-uniform exposure to direct solar radiation can cause variations in pedestrians' instantaneous thermal sensations, and dynamic thermal experiences can lead to the formation of memorized thermal sensations, causing a deviation between instantaneous and whole-trip thermal sensations. There is a significant correlation between pedestrians' mean skin temperature and heat storage and their thermal experiences over the past 10–25 min. Regression analysis provided different weights that could represent the memory component in whole-trip thermal sensations. The findings provide a theoretical basis for understanding pedestrian thermal comfort in dynamic outdoor environments and will help improve the thermal quality of outdoor travel spaces.

Impact of ENVI-met-Based Road Greening Design on Thermal Comfort and PM2.5 Concentration in Hot–Humid Areas

Road greening markedly impacts road thermal comfort and air quality. However, previous studies have primarily focused on thermal comfort or PM2.5 individually, with relatively few addressing both aspects comprehensively, particularly in humid regions. This study combined field measurements and simulations. It employed physiological equivalent temperature (PET) and quantified the horizontal distribution of particulate matter 2.5 (PM2.5). The research examines the effects of planting spacing, tree species, and tree–shrub combinations on pedestrian walkways in humid climates during both summer and winter. Using measured tree data and road PM2.5, a plant model was established and pollution emission parameters were set to validate the effectiveness of the ENVI-met through fitting simulations under various scenarios. The results indicated that (1) plant spacing for trees influenced both the road thermal environment and PM2.5 levels. Smaller spacing improved thermal conditions but increased PM2.5. (2) trees with large canopies and high leaf area indices (LAIs) notably enhanced thermal comfort, while those with smaller canopies and dense understories facilitated PM2.5 dispersion. The 3 m spacing resulted in a maximum absolute PM2.5 concentration difference (C) of 5.05 μg/m3 in summer and a maximum mean absolute PM2.5 concentration difference (M) in the downwind region of 2.13 μg/m3 in winter. (3) Combining trees with shrubs moderately improved pedestrian thermal comfort. However, taller shrubs elevated PM2.5 concentrations on walkways; heights ranging from 1.5 m to 2 m in summer showed higher C values of 5.38 μg/m3 and 5.37 μg/m3. This study provides references and new perspectives for the optimization of roadway greening design in humid areas in China.

An Investigation of Globe Temperature in Street Canyons: A Scaled Model Study Implementing Cool Materials

The measurement of globe temperature (GT) is essential for investigating pedestrian thermal comfort in street canyons. The globe thermometer is the most common instrument used to measure GT; however, its application in scale models has not been thoroughly investigated to date. Therefore, this study explicitly investigates globe thermometer measurements in scale models and analyzes the need for customization of the globe thermometer for more reliable measurements. Scaling down with respect to the size of the globe thermometer and the effect of solar orientation/envelope materials are investigated in this study. The initial experiments were carried out in an outdoor setting using a typical street canyon model (scale 1:100) with an east-west street orientation. The results of the experiment are presented to compare a low solar reflectance street canyon (albedo of 0.4) and a high solar reflectance canyon (albedo of 0.6) in terms of surface temperatures, heat flux, and globe temperature. It is observed that although the wall and road surface temperatures are lower for the high solar reflectance canyon compared to those for the low solar reflectance canyon, the GT (measured at pedestrian height) is higher in a high reflectance canyon during the daytime, which could be due to the combined effect of direct radiation and short-wave reflection. However, for the hours after sunset, a reverse effect is observed, i.e., the GT becomes lower (up to 0.8 °C) in the case of a high reflectance canyon compared to that for the low reflectance canyon. Furthermore, the study emphasizes the impact of solar reflectance of canyon surfaces on GT values, due to the view factors that the globe thermometer on those surfaces.

Clustering Micromobility Devices based on Speed and Comfort

Pedestrians and micromobility devices are grouped into 4 clusters with increasing speed and decreasing comfort. The Clusters are assigned a Path User Comfort Equivalent (PUCE) factor which can be used in pathway design to adjust volume impacts on pedestrian comfort. Clusters 1 (including skates and mobility aids), 2 (non-motorized cycles), 3 (most motorized devices), and 4 (moped-style scooters) have PUCE of 1.0, 2.1, 2.8, and 4.0 respectively. Scenario analysis shows that most pedestrians would still feel comfortable with a large shift from Cluster 2 to Cluster 3 (i.e., bicycle electrification), but that increasing device speeds would substantially degrade pedestrian comfort.

Discomfort in pedestrian-electric scooter interactions during frontal approaches

BackgroundAs urban landscapes rapidly integrate e-scooters into their transportation ecosystems, understanding pedestrian-e-scooter interactions becomes paramount for safety and planning. This study investigates pedestrian discomfort levels and avoidance strategies when encountering an e-scooter approaching from the front. Methods25 participants were exposed to e-scooters approaching at three different speeds and lateral distances. Avoidance paths were plotted, and subjective discomfort levels were recorded and analysed. ResultsOur findings underscored two key behaviours: 1) As the speed of the e-scooter increased, participants initiated avoidance manoeuvres from a further distance ahead, suggesting a heightened perception of risk. 2) Regardless of the e-scooter's speed, the lateral distance maintained during passing remained fairly constant. However, when the e-scooter's initial lateral position was closer to participants, both the initiation distance for avoidance and the reported discomfort level increased noticeably. ConclusionThe findings underscore the critical influence of lateral distance and e-scooter speed on pedestrian comfort and avoidance behaviour. These insights can guide urban planners and policymakers in designing safer and more efficient shared spaces.

Evaluation of an immersed boundary numerical framework to address the wind field in complex urban topographies

Estimating the wind velocity field in an urban area is important for pedestrian comfort and safety, as the local wind velocities dictate the transport of heat and air pollution in urban environments. Therefore, it is an essential requirement to assess wind patterns when designing urban areas. Computational Fluid Dynamics (CFD) numerical solvers are usually employed to estimate the wind comfort in an urban area under different wind intensities and directions. However, CFD simulations are expensive in terms of time, especially when many scenarios are addressed to ensure safety and comfort for multiple conditions. Here, a CFD framework based on an immersed boundary approach to discretize the urban topography is developed and validated against experimental data in a wind tunnel and two different standard body-fitted mesh codes. The new solver employs a structured cartesian octree grid automatically generated from Lidar data of urban topographies. The advantages are eliminating the complex and time-consuming pre-processing of urban topographies and making the framework accessible to urban planners without CFD expertise. Furthermore, the code is equipped with GPU parallelization that further reduces the computational time. Provided that the best practice guidelines for urban simulations are satisfied, in particular at least 10 cells between two buildings, the code shows very good agreement in all the tests comprising of a simplified and real urban neighborhood highlighting the importance of accurately solving the complex terrain topography of an urban region when non-negligible elevation changes of the order of 20/40 meters are present.

‘Robinson’ Pedestrian Bridge in Budapest, Hungary

Abstract‘Robinson’ Bridge was built as part of the National Athletic Centre project in Budapest, Hungary. The 168 m long cable‐stayed pedestrian bridge has a 65 m tall inclined pylon standing on a small island. The 12,72 m wide main girder is suspended to a monopylon with a two‐plane fan‐shaped FLC stay cable system. The landmark bridge's stunning appearance was achieved with hybrid structures. Both the pylon and parts of the slender stiffening girder were made of S460 steel tubes filled with concrete to enhance their load‐bearing and dynamic characteristics. Due to very limited construction area, a special erection process was used for the pylon involving a 200t floating crane. The stiffening girder was built with incremental launching. Cable tensioning with a curved deck proposed special design challenges. Large displacements had to be accurately predicted. To meet the strictest requirements for pedestrian comfort, TMDs were applied and dynamic load tests carried out to prove the results.

The effects of acoustic-light-thermal environment quality parameters on pedestrians’ overall comforts in residential districts

This study explored subjective responses towards various environmental quality parameters. It would be helpful to approach an overall comfort improvement relating to physics. In order to investigate the combined effects of sound, light and heat on the overall comfort of pedestrians, which could be evaluated by overall comfort vote, two residential areas in Yubei District, Chongqing (a Cfa city in China) were selected for field measurements and questionnaires. Three were three key findings were concluded based on subjective responses to environmental parameters via multiple linear regression. First, the average outdoor neutral temperature, mean neutral sound level and neutral illumination intensity were determined to be 26.6 °C (determined by physiologically equivalent temperature), 56.5 dBA (determined by A-weighted equivalent continuous sound level) and 21.4 klx (determined by LUX), respectively. Second, considering the effects of both physiology and psychology, thermal perceptions varied for acoustic and light environments. Residents partially had lower neutral temperatures at the noisy condition. Third, environmental quality factors had a significant effect on overall comfort. Positive correlation between physiologically equivalent temperature and overall comfort vote was found (sig < 0.000); while the effects of sound pressure and light intensity were not always significant. Hence, thermal stress played a significant role in people’s overall comfort. This study has explored the effects of three environment quality parameters on human perceptions. It provided better understanding against dwellers’ feelings under complex circumstances. Future urban design and planning works should consider the cooling factors regarding contextual acoustical and visual environments.

Modelling the effects of neighbourhood and street geometry on pedestrian thermal comfort in Hong Kong

The severe global warming and rapid urbanization increase the risks of extreme heat stresses for pedestrians. While urban geometry significantly affects pedestrian thermal comfort, limited research has explored the relative impacts of street and neighbourhood design. ENVI-met simulation models were constructed to analyse their effects on pedestrian thermal comfort in an urban street of Hong Kong. Subsequent ANOVA analysis revealed that surrounding building height was a major contributor to thermal comfort variations of a street in addition to street orientation and aspect ratio, while tree coverage ratio and ground albedo played much weaker roles. Based on these, a multivariate model has been developed to predict hourly street thermal conditions for various street orientations, aspect ratios and surrounding building heights. Specific preferred and avoided street configurations for optimizing the thermal environment have been identified. For instance, aspect ratio ≥ 5.0 is preferred for NW-SE Street with surrounding building height of 45–105 m.

The Design Concept of Integrated Pedestrian Sidewalk with Solar Plants as a Form of Green Campus Development at the Bali Land Transportation Polytechnic

Abstract An important aspect of creating a viable campus environment is providing safe and comfortable walking paths. Proper walking paths give some advantages for students, including improved physical and mental health, transportation efficiency, and increased Student satisfaction and happiness. The pedestrian sidewalk area at Bali Land Transportation Polytechnic (Poltrada Bali) covers 3800 m2, experiencing high pedestrian activity but lacking protective roofing to enhance pedestrian comfort. Based on the pedestrian sidewalk area, a solar power plant as support for the green canopy construction combined with shading vines is possible. The generated electrical energy serves as the power source for the Public Electric Vehicle Charging Stations (PEVCS) in the campus parking lot as a support for the electric vehicle acceleration program in Bali province. In addition to PEVCS, energy extraction surplus is used as alternative energy for street lighting facilities in the campus area. In this study, the design concept of a shaded pedestrian sidewalk has been carried out, with multiple benefits as solar plants using Delphi as a variable identification and validation tool, and SketchUp software to visualize design shapes aesthetically. The results show that a pedestrian comfort level of 94% was obtained and the maximum power generation of 934,800 Wp, thus it was able to meet the 887,832 W campus operational power reserve needs, street and garden lights of 9,728 W, and the power requirements of two PEVCS units of 22,000 W with a surplus of 15,240 W electric power.

The impact of twisted wind on pedestrian comfort around two non-identical-height buildings in tandem arrangement: a wind tunnel study

Due to the impact of urbanization, an increasing number of buildings are being constructed near hilly terrains because of the limited availability of land resources. The influence of twisted wind profile (TWP) on pedestrian-level wind comfort surrounding two tandem non-identical-height buildings, with a height ratio H1/H2 ranging from 3:1 to 1:0.33, was investigated by wind tunnel experiment with two twist angles (13 ° and 25 °), and compared with the conventional wind profile (CWP). The assessment of thermal comfort was based on Physiologically Equivalent Temperature (PET) using wind velocity measured from the wind tunnel and observation results. Both the mean and gust wind velocities were investigated and compared with wind assessment criteria. The results reveal a significant disparity in the mean and gust wind fields for various H1/H2 under both CWP and TWPs, with the influence of twist being more pronounced for step-up building configuration (H1<H2). The influence of TWPs on the low wind velocity region demonstrated contrasting patterns for buildings with step-up and step-down configurations. The pedestrian level wind environment varies significantly with H1/H2 under CWP and TWPs in the passage between the two tandem buildings, categorized as “Sitting long” for identical-height buildings and modified to “Strolling” and “Walking fast” for step-up building configuration. The twisted wind shifts the “Sitting short” area toward the direction of the approaching twisted wind flow and amplifies the “Strolling” area on the other side. The twisted wind can diminish the thermal comfort surrounding the two tandem structures during summer while enhancing the thermal environment in winter.

Integrated effect of aspect ratio and tree spacing on pedestrian thermal comfort of street canyon.

Increasing heat stress in urban environments due to climate change has a significant adverse impact on human work and daily life. Street canyons as the main component of the underlying surface of the city and the main place of residents' activities, a comprehensive understanding of street morphology and tree planting practices can help to improve thermal comfort. Based on survey data and field experiments, this study designed 30 scenarios and employed ENVI-met model (version 5.0.3) to quantify the effect of street aspect ratio (H/W: H is building height and W is street width) and tree spacing (TS) on pedestrian thermal comfort in two differently oriented streets (north-south and east-west) in Taiyuan, China. Results showed that H/W ratio and TS significantly influenced the street thermal comfort mainly owing to shading. H/W ratio played a pivotal role in reducing mean radiant temperature (Tmrt) and physiological equivalent temperature (PET), and was negatively correlated with Tmrt and PET. Compared to no-tree scenarios, street trees significantly improved thermal comfort (mean reductions of Tmrt and PET were 12.74℃ and 5.66℃, respectively), and PET and Tmrt were significantly negatively correlated with TS. The improvement effect of street trees on Tmrt and PET in east-west oriented street was better than north-south oriented street. H/W = 1.0 and TS = 6m appeared as the proposed combination to mitigate the summer thermal comfort in the temperate monsoon climate zone. These quantitative results provide new insights into renewal and design strategies for future urban planning.

Adversarial image-to-image model to obtain highly detailed wind fields from mesoscale simulations in mountainous and urban areas

The characterisation of wind is of great interest in multiple disciplines such as city planning, pedestrian comfort and energy generation. We propose a conditional Generative Adversarial Network (cGAN), based on the Pix2Pix model [1], that can generate detailed local wind fields in areas with complex orography or an urban layout, which are comparable in level of detail to those from Computational Fluid Dynamics (CFD) simulations, from coarser Numerical Weather Prediction (NWP) data.

Pedestrians' safety using projected time-to-collision to electric scooters

Safety concern among electric scooter riders drives them onto sidewalks, endangering pedestrians and making them uncomfortable. Regulators’ solutions are inconsistent and conflicting worldwide. Widely accepted pedestrian safety metrics may lead to converging solutions. Adapting the time-to-collision from car traffic safety, we define projected time-to-collision and experimentally study pedestrians’ objective and subjective safety. We design isolated and crowd experiments using e-scooter-to-pedestrian interactions to assess the impact of various factors on objective safety. In addition, we conducted a pedestrian survey to relate the subjective safety and the metric. We report a strong correlation between subjective safety and the projected time-to-collision when agents face each other and no relation when the e-scooter overtakes a pedestrian. As a near-miss metric correlated with pedestrian comfort, projected time-to-collision is implementable in policy-making, urban architecture, and e-scooter design to enhance pedestrian safety.

Wind characteristics around a skyway bridge of high-rise buildings

To respond the expansion of urban centers, the proliferation of high-rise buildings demands a better understanding of the aerodynamic phenomena around skyway bridges connecting these structures. This analysis, utilizing the advanced computational fluid dynamics verified by wind tunnel test data, investigates the wind characteristics around such bridges, crucial for structural stability, pedestrian comfort, and aerodynamic efficiency. This study focuses on the interactions between a 2 × 2 building array with a building height-to-street width ratio of 30 and a skyway bridge, investigating those factors such as bridge influence, building structures, building height, and bridge position. Using the three-dimensional steady Reynolds-averaged Navier–Stokes equations along with the Reynolds stress model for turbulence closure, the results show that the presence of skyway bridge significantly modifies local wind patterns. Wind speed and turbulence intensity are impacted differently based on the bridge's upstream or downstream settings. Downstream bridges tend to reduce wind speeds due to the sheltering effects, while upstream placement of bridge can enhance wind flow, affecting both the structural design and pedestrian comfort. Additionally, building height variations adjacent to the bridge influence wind velocity and pressure profiles, with taller buildings intensifying wind speeds at lower levels because of the channeling effects. These insights are pivotal for optimizing the skyway bridge designs to improve airflow distribution, enhance environmental sustainability, and ease wind-caused disturbances, offering a guideline for future architectural and urban planning in high-rise districts.

Digital Twin and Wearables Unveiling Pedestrian Comfort Dynamics and Walkability in Cities

Digital Twin and Wearables Unveiling Pedestrian Comfort Dynamics and Walkability in Cities

Psychological influence of sky view factor and green view index on daytime thermal comfort of pedestrians in Shanghai

Human outdoor thermal comfort is a complex perceptual process influenced by various factors, among which much attention has been given to physiological response, underscoring the need to equally focus on psychological perception. This study examines the psychological effects of Sky View Factor (SVF) and Green View Index (GVI) on pedestrian thermal comfort across spaces with similar microclimate, by conducting field surveys, climatic measurements, and a questionnaire survey involving 87 participants on October 22, 2022 in Shanghai. The results indicate that differences in SVF of about 8.6% and GVI of about 23.0% among independent points, as well as over 7.9% changes in GVI during a journey, significantly affect thermal sensation (p < 0.05, providing statistically significant evidence that these results are unlikely due to chance). Furthermore, the study suggests that under the influence of SVF and GVI, the general thermal sensation is influenced by the thermal sensation of the last point, as well as the averages and extremes (p < 0.001, p < 0.05, p < 0.001, respectively), while general thermal satisfaction correlates with average satisfaction levels (p < 0.05). These insights highlight the necessity of strategically designing SVF and GVI in urban outdoor spaces and offer valuable guidelines for urban planning to optimize pedestrian thermal comfort.

Machine Learning for Pedestrian-Level Wind Comfort Analysis

(1) Background: Artificial intelligence (AI) and machine learning (ML) techniques are being more widely employed in the field of wind engineering. Nevertheless, there is a scarcity of research on the comfort of pedestrians in terms of wind conditions with respect to building design, particularly in historic sites. (2) Objectives: This research aims to evaluate ML- and computational fluid dynamics (CFD)-based pedestrian wind comfort (PWC) analysis outputs using a novel method that relies on the sophisticated handling of image data. The goal is to propose a novel assessment method to enhance the efficiency of AI models over different urban scenarios. (3) Methodology: The stages include the analysis of climate data, CFD analysis with OpenFOAM, ML analysis using Autodesk Forma, and comparisons of the CFD and ML results using a novel image similarity assessment method based on the SSIM, MSE, and PSNR metrics. (4) Conclusions: This study effectively demonstrates the considerable potential of utilizing ML as a supplementary tool for evaluating PWC. It maintains a high degree of accuracy and precision, allowing for rapid and effective assessments. The methodology for precise comparison of two visual outputs in the absence of numerical data allows for more objective and pertinent comparisons, as it eliminates any potential distortions. (5) Recommendations: Additional research can explore the integration of ML models with climate data and different case studies, thus expanding the scope of wind comfort studies.

A design workflow for effective solar shading of pedestrian paths

Shading pedestrian paths is strategically important to ensure accessibility and comfort for pedestrians in cities. Limited applicability in practice of previous research about the effectiveness of natural and artificial shading devices was found. This paper proposes a workflow to design effective installations of shading devices on sidewalks; it relies on a design tool developed prioritising compatibility with other software/processes for its application to urban design. The methodology was tested on the city of Milan; the performance of 60 % linear path in shade was set as the design goal. Based on solar radiation exposure of urban canyons, a time of the day was associated with each simulated summer scenario. A library of shading devices was compiled allowing designers to test various proposals. The workflow was applied at first to theoretical urban canyons, then to a real case study sidewalk. Results included a catalogue of solutions with installation guidelines, a table to estimate the recommended number of shading devices for each sidewalk location, and the opportunity to iteratively test master planning proposals. Four applications of the workflow were proposed in response to resources availability and increasing outcome suitability. The workflow would support urban designers in implementing solar radiation exposure analysis in their practice.