An observational analysis of shade-related pedestrian activity

2.1 Study framework

This study examined the possible impact of shade on pedestrian travel in thermally stressful environments by collecting a large sample of observational data on pedestrian activity in Tel Aviv-Yafo in the summer of 2020. A systematic monitoring of a large sample of pedestrians was deployed in multiple urban locations with a wide variety of morphology, functionality and size of usable space.

The hypothesis was, given comparable options of unshaded and shaded spaces in a hot and sunny environment, that most people would travel in the shade.

The term pedestrians is defined here as those who travel by foot power. Therefore, the term refers to people who travel by walking, cycling or using any other foot-powered micromobility vehicle (here the terms bicyclist or cyclist all refer to a person riding a foot-powered/semi-foot-powered wheeled vehicle such as a bicycle, scooter or electric bicycle). Pedestrians were observed on city sidewalks, bicycle lanes and public open space throughways which had a clear option between travelling in the shade or in an unshaded space.

An important factor to consider in the methodological development of this study is the nature of shade in an urban space. Shade in urban areas is highly temporal due to the movement of the sun throughout the day and the narrow configuration of streets (in contrast to a dense forest or an open field). The shading configuration of a street will depend on the directional orientation of a street in relation to the movement of the sun, as well as the presence, size, shape and location of shade-causing structures such as trees, buildings, pergolas, covered walkways, etc. The amount and location of shade on a street may change quickly over time, often in less than an hour. This meant that monitoring periods needed to be kept quite short to ensure that the size and location of the shaded and unshaded spaces would remain relatively constant throughout monitoring.

Additionally, due to the complex nature of cityscapes, city walkways and urban shade, the authors chose to collect a large sample size of pedestrians from a large number and variety of sites within the study area of Tel Aviv-Yafo. The variety of urban morphologies and locations was essential to overcome the problem of generalising insights from only a single or a handful of observed urban configurations or from a small population dataset.

2.2 Monitoring sites

Tel Aviv-Yafo, a coastal city located on Israel’s Mediterranean coastal plain (32°5′ N 34°48′ E), has a population of about 475,000 residents and a municipal area of 52 km². The city has 843 linear-km of vehicular roadways and 178 km of largely on-sidewalk bike paths (Center for Economic and Social Research 2023). However, as was observed in this study, it is common for cyclists to travel on sidewalks (pedestrian pavements) both on and off the bike paths, likely because the paths cover only certain parts of the city and are not always located on both sides of the street. Regarding the types of transit used by residents, it was found in a survey that, in 2020, 16% of commuters used bicycles, 12% of commuters travelled by walking, 14% travelled by public transit, and the rest travelled by private motor vehicle. Although nearly 80% of resident households owned cars, 53% of residents said they used walking as one of their three main forms of leisure and non-work-related transit, and 36% of residents reported cycling (Municipality of Tel Aviv-Yafo 2024).

Tel Aviv-Yafo’s hot season spans half the year from May to October, with an average daily maximum temperature of about 30°C in July–September. The city has approximately 3300 annual hours of sunshine, and from late March to late September the average daily global radiation (GR) is > 7 kWh/m²; the average maximum daily irradiance ranges from 889 to 1018 W/m². The city’s average annual precipitation is 524 mm, with almost no rainy days from the beginning of May to late September (Israel Meteorological Service 2021). During the study period, the average sunrise occurred at approximately 05:50 and sunset at 19:25 hours, with solar noon at around 12:40 hours local daylight savings time (DST/UTC + 3:00) (NOAA 2024).

Pedestrian activity was monitored on sidewalks and public walkways in central Tel Aviv-Yafo in the summer. Visual and microclimatic data were simultaneously collected at each of a series of 34 monitoring sites (Table 1 and Figure 1) during periods ranging from 10:00 to 17:00 hours DST, over the course of eight separate days. Monitoring was conducted on weekdays, approximately once a week, from 5 July to 1 September 2020. The monitoring sites were comprised of 29 distinct locations, each of which was monitored one to three times. At the repeated monitoring locations, site circumstances varied according to time of day, pedestrian presence, micrometeorological conditions or amount of available shade, and therefore these were considered separate ‘sites’. Pedestrian traffic at individual sites was continuously monitored for periods averaging 20–30 min, using a tripod-mounted camera with a high-frequency frame rate (as detailed below).

Figure 1

The monitoring sites were selected based on shade maps produced in a recent study in Tel Aviv-Yafo by Aleksandrowicz et al. (2020). Locations were also chosen based on sites with a variety of morphological and functional properties across the different sites, clear and distinct options for shaded travel and unshaded travel, and sufficient volume of pedestrian traffic for robust statistical analysis. The spatial clustering of selected sites within Tel Aviv-Yafo reflects the structure of the existing urban fabric, which is not geographically homogenous, and allowed the maximisation of the observation of streets and public spaces which are actively used by pedestrians and offered options for walking and cycling route choices.

The various monitoring sites encompassed different areal proportions of usable shaded and unshaded public open space for pedestrian traffic. Therefore, to refine the analysis, the monitored sites were divided into three categories according to the relative area of shaded space available for pedestrians. Table 2 describes these three shade availability categories: category 1 contains more unshaded than shaded space; category 2 has a relatively even distribution of shaded and unshaded space; and category 3 has more shaded than unshaded space. Figure 2 illustrates the respective shade availability categories. The shade availability categories are based on the ratio of shaded versus unshaded space at a given site at a specific point in time; therefore, they refer to the noted ratio within the pedestrian travel space (i.e. sidewalk) at the time of the monitoring period for each site. Note that categories 1 and 3 may encompass a wide variety of scenarios; e.g. sites identified as category 1 may have a moderately high proportion (60–70%) of unshaded space or be exposed to direct sun over 90% of the available space—leaving only a narrow strip of sidewalk in the shade. In addition, the total available pedestrian space may either include a single sidewalk or be distributed over two sidewalks on either side of the street. While data were originally collected at 75 sites, upon later analysis of site photographs, 41 of the sites were eliminated due to a lack of clear choice between unshaded and shaded space or for other analysis-related issues.

Figure 2

2.3 Pedestrian counting

A variety of different pedestrian counting methods were considered for data collection; the most accurate option was found to be the use of ‘screenlines’, i.e. precise markings embedded in the photographic images signifying the line where, once crossed travelling in either direction, pedestrians were counted (Nordback et al. 2018; Schneider et al. 2009). This allowed the extraction of information from large sequences of images, without the risk of over- or under-counting individual pedestrians.

Street activity was documented using high-frequency automated photography, with a single tripod-mounted digital Panasonic Lumix S1R camera capable of recording sequences at 2-s intervals at high resolution (4272 × 2848 pixels, compressed to 2136 × 1424 to minimise storage and transfer time). After initial processing and filtering of approximately 40,000 photographs, manual counts of pedestrians were performed on selected images using screenlines inserted into the images to mark counting locations (Figure 3). These screenline-based counts allowed a comparison to be made of the number of pedestrians travelling at a given point in time in shaded and unshaded spaces: as individuals crossed the blue screenline, they were identified as travelling in the shade, and those crossing the yellow screenline were identified as travelling in the unshaded space. A technical limitation was that automobile traffic often blocked the view of the far side of the street, but the high frequency of imaging allowed the counting of obstructed pedestrians before or after crossing the screenlines.

Figure 3

While the primary focus of this research was walking activity, cycling activity was also examined by counting cyclists, thus increasing the overall sample size and improving the reliability of the analysis. The cyclist count was recorded separately, however, so that the two types of data could be compared. Following the primary pedestrian count, a subset of the data was examined by gender, in relation to the propensity for shaded travel.

2.4 Microclimate monitoring

A fixed rooftop microclimatic measurement station was used to monitor background meteorological variables, and to ensure that monitoring was taking place on typical clear-sky summer days. It is important to note that the station was not intended as a means of measuring pedestrian-level thermal comfort. This measurement station was installed 2 m above the roof of a five-storey municipal building (about 24 m above ground level) in central Tel Aviv-Yafo (Figure 1). The instrumentation consisted of a compact multi-sensor setup (Gill GMX501) which provided readings of air temperature (°C) and relative humidity (%) at 5-min intervals, as well as wind speed (m/s) and direction, and global solar radiation (W/m²) at 15-s intervals. The set-up was connected to a Campbell CR300 data logger charged using a fixed photovoltaic panel.

Across all monitoring days, weather conditions were relatively consistent, as is typical of the summer climate on the eastern Mediterranean coast. Daytime conditions were generally clear and sunny, with temperatures in the range of 28–33°C and relative humidity in the range of 60–85%. Peak GR was 1040 W/m²; wind speed at the station generally ranged from 2 to 5 m/s.

3.1 Shade availability and pedestrian counts

After classifying the data according to shade availability categories, a clear pattern emerged by which the proportion of people travelling in shaded areas is directly correlated with the relative amount of shaded space (Figure 4). While this basic relationship is as expected, it is notable that even in locations with more unshaded space (category 1, n = 1734), nearly half of all pedestrians travelled in the shade (44%), and at locations with approximately equal amounts of shaded and unshaded space (category 2, n = 2575), nearly two thirds (64%) of pedestrians travelled in the shade. Finally, at sites with more shaded space (category 3, n = 954), a full 80% of pedestrians travelled in the shade. Thus, the density of pedestrian traffic was clearly higher in the shaded areas than in areas exposed to direct sun. There is some variation in the percentages between cyclists and walkers: at sites with less shade, 46% of walkers and 37% of cyclists travelled in the shade; at evenly shaded/unshaded sites, 68% of walkers and 51% of cyclists did; and at more-shaded sites, 72% of walkers and 94% of cyclists were in the shade. This variation can be attributed to the distribution of bicycle lanes. As previously noted, cyclists in Tel Aviv-Yafo often travel on sidewalks even when bicycle lanes run alongside them, while walkers often avoid bicycle lanes.

Figure 4

3.2 Comparability of sites

Among the locations with an approximately equal distribution of shaded and unshaded space (category 2), the data were filtered according to functionality and general appeal of the built environment to identify sites which could be attractive to pedestrians in the shaded and unshaded spaces, at a relatively comparable level, in relation to non-micrometeorological aspects. The aspects examined included the presence of retail storefronts, amenities such as bus stops or public seating, sidewalk width or likewise amount of travel space, and the quality of the public open space. Six monitoring sites (n = 1791) were determined to have not only equal amounts of shaded and unshaded space but also equal functionality and appeal of the immediate built environment in both the shaded and unshaded areas (Figure 1, sites Tb8.a, Tb8.b, Td26, Te31, Tg47 and Ti58).

At these six most comparable sites, 67% of all pedestrians (n = 1791) and 71% of those walking (n = 1297) travelled in the shade—much higher percentages than for the overall sample. Interestingly, only 56% of cyclists travelled in the shade (n = 494); this lower proportion may be due to two of the six sites having on-sidewalk bicycle lanes, both of which were unshaded (Table 3). To determine whether there was a connection between shade, travel activity and gender, the relative numbers of men and women were examined at the most comparable sites. The population was evenly split by gender (50.5% of the sample were women), and in both cases, 67% of men and women travelled in the shade.

3.3 Solar exposure

To gauge more precisely the effect of environmental conditions on pedestrian movement, the authors examined the relationship between the intensity of solar exposure during observation periods and propensity to walk in the shade. Pedestrian solar exposure was calculated based on incoming GR measured simultaneously at the fixed station, accounting for both direct and indirect shortwave radiation components. The intensity of the direct radiation component, estimated as 85% of GR with assumed clear skies, was calculated according to the angle of incidence (based on latitude, date and time of day) on a standing person, modelled as a rotationally symmetrical body. The diffuse component was estimated assuming a sky view factor representing an open and fully exposed area, and the reflected component was similarly quantified assuming a ground surface albedo of 0.2 (for further description of this calculation method, see Pearlmutter et al. 2006). The calculation was performed only for walking pedestrians, as the geometric properties are less applicable to cyclists, and only for monitoring sites where a minimum of 100 walking pedestrians were observed (a rate of 3.3 pedestrians/min). Two outlier locations were removed due to functional anomalies.

In these higher traffic sites, a strong positive relationship (R² = 0.65, p < 0.05) was observed between the intensity of solar exposure and proportion of pedestrians walking in the shade (Figure 5a). In other words, as the intensity of thermal stress due to a lack of shade increased, so did the proportion of pedestrians observed to be walking in the shade. At locations where < 50% of pedestrians were observed walking in the shade, the level of solar exposure during the observation period was relatively low (≤ 300 W/m²)—such that being exposed to direct sun in these cases would be less thermally stressful, and the benefit of walking in the shade would be less pronounced.

Figure 5

The same pedestrian traffic data were also analysed in relation to global solar radiation (i.e. measured on a horizontal surface without considering the angle of direct solar rays relative to a standing person’s body) and average ambient air temperature (Figure 5b and 5c, respectively). The results show a very weak relationship (low R² values) between the percentage of pedestrians in the shade and either GR on an upward-facing horizontal surface (Figure 5b) or measured air temperature (Figure 5c). This is in sharp contrast to the strong relationship shown in Figure 5a for calculated solar exposure on a standing human body. Regarding the relationship with air temperature (Figure 5c), the weakness of the correlation reflects the fact that the overall range of variation in air temperature between sites and observation periods is quite small (approximately 4°C), in contrast to the range of radiative heat stress due to solar exposure across shaded and unshaded locations.

4.1 Factors influencing shade-related pedestrian activity

Countless factors can influence pedestrian route choice and travel behaviour, such that isolating the influence of shading and thermal comfort is a challenging endeavour (Tong & Bode 2022). However, considering that from a sample of over 5000 pedestrians, 60% travelled in the shade—and that at sites with a relatively equal availability of shaded and unshaded spaces and similar site appeal and functionality, the percentage walking in the shade rose to > 70%—it can be surmised that pedestrians on hot and sunny urban streets are indeed systematically influenced by shade in their decisions, whether out of conscious intent or instinctive response to environmental stimuli.

While this finding may initially appear self-evident, it represents an important phenomenon that needs to be scrutinised and documented quantitatively. In a system as complex as a city, there will always be a multitude of factors that influence behaviour in diverse ways, such that establishing the extent to which people behave according to a predicted logic is valuable for understanding urban dynamics, and for planning more effectively in response. Previous studies examining the impact of shade on pedestrian behaviour have not generally considered the actual availability of shaded versus unshaded space at urban sites, and the present results suggest that the amount of shaded space has a direct impact on the percentage of people who use it.

Regarding mode of transportation, there was a small difference in the full sample between the percentages of people walking and those cycling in the shade. This is surprising, considering that cyclists generally travel faster, enjoy the cooling effect of greater wind speeds, and therefore experience quite a different thermal sensation. However, a higher rate of people walking rather than cycling in the shade was observed in the most comparable sites.

Beyond the mode of transportation and quantity of shaded space, the actual intensity of a pedestrian’s exposure to solar radiation at a given point in time also appears to be a determinative factor in shade-related route choice. A strong positive relationship was seen between the level of bodily solar exposure in unshaded areas and the percentage of pedestrians walking in the shade. This relationship was not reflected when data for air temperature or even GR were examined. Rather, it was solar exposure calculated with reference to directional incidence on an upright person’s body that emerged as a consequential factor. This suggests that when bodily solar exposure levels are higher, pedestrians do experience greater thermal stress and are more attuned to opportunities for shade travel.

The identified relationship between pedestrian activity and solar exposure (but not GR) emphasises the complexity involved in quantifying conditions of human thermal comfort, as a discrete analysis of how microclimatic conditions affect the body was an essential part of identifying the correlation between environmental and activity-related data. Ultimately, this connection serves as a reminder that to analyse the various design-related aspects of thermal comfort, we must be aware of what the full human experience of an environment encapsulates.

It is worth considering that the experience of thermally stressful environments varies greatly by geographical location, whether in Nagoya (Watanabe & Ishii 2016), where only 50% of pedestrians were observed stopping in the shade on hotter days, or in Austin (Kim & Brown 2022), where the proportion travelling in the shade was as high as 81% in summer. In such locations, both the intensity of heat stress and cultural attitudes towards heat and sun exposure may be different from those in the Mediterranean basin and Middle East. Such ‘climatocultural’ factors have been shown to systematically affect outdoor thermal perception (Brychkov et al. 2018)—and in practice, of course, many other factors not related to the thermal environment shape pedestrian movement patterns as well.

4.2 Policy implications

The results show that > 70% of walking pedestrians travelled in the shade at the most reliably comparable sites. If more sidewalks and public open spaces in overheated cities are well-shaded, then people are more likely to use them. Likewise, lack of shaded travel areas on hot days may discourage some people from choosing to travel by foot, leading them to choose motorised transport and spend more time in air-conditioned spaces. This study provides quantitative evidence of the importance of shade for pedestrian travel, which policymakers can use to advocate for the importance of shade.

A recommendation for urban planners and policymakers is to set specific shade requirements in urban areas prone to extreme heat. As the shade availability categories demonstrate, and as a recent set of shading guidelines for Israel presents, determining a necessary quantity of available shaded space on sidewalks and public open spaces throughout the day, during the hot season, may ensure that pedestrians have sufficiently shaded travel ways (Aleksandrowicz et al. 2025).

4.3 Limitations

This study was limited by several factors. First, the volume of street traffic was likely affected by the COVID-19 pandemic (Ugolini et al. 2020), though restrictions on movement during the time of data collection had largely ended and presumably the proportion of people found in the sun or shade was not affected. Second, only locations in which there was a clear option between travelling in a shaded and unshaded space could be examined systematically, thus excluding many potential observations sites. The definition of ‘shaded’ and ‘unshaded’ space is not always precise, as trees may provide dappled shade and there may be gaps of varying distance between them, and even shadows from solid structures may be irregularly shaped and differ in the degree of shading they provide. This limitation was addressed by eliminating ambiguous sites from the analysis; however, some variability between locations with similar shade availability grades still exist. At sites with more than two travel options, such as a boulevard with two sidewalks and a middle pathway, screenlines were applied to the two most clearly defined shaded and unshaded paths. This maintained the binary comparison used elsewhere while increasing site variety. The gender-related pedestrian count was performed using purely visual observation, and therefore it is possible that gender was misattributed in certain cases.