Walkability and thermal comfort: an integrated evaluation system

Keys factors of walkability

Several urban design theories explored walkability at the neighbourhood scale and street level. That essentially considered physical features to improve the walking experience. According to Forsyth (2015), many studies analyzed the physical facilities and conditions that allowed walking, such as accessible areas, compact cities, and physically–enticing or safe. Others characterize the walkable environments’ outcomes or performance by improving sustainable transportation modes, making outdoors friendly and animated or enhancing exercises. Finally, some studies focused on identifying walkability as a proxy to improve urban environments using measurement tools. That can strengthen walkability and solve many urban problems. This section presents the most used indicators at the neighbourhood scale and the street level. 

At the neighbourhood scale

Many studies have investigated macro-level indicators at the neighbourhood scale to improve walking rates in urban areas (Habibian and Hosseinzadeh, 2018; Hall and Ram, 2018; Taleai and Taheri Amiri, 2017). Other studies have attempted to address key elements that help create a pedestrian-friendly neighbourhood (Wang and Yang, 2019) by considering important safety, comfort and convenience indicators (Aghaabbasi et al., 2017; Landis et al., 2001; Ussery et al., 2019). The neighbourhood microscale level is essential to identify pedestrian amenities within the walking environment’s quality (Aghaabbasi et al., 2017). The listed factors were coordinated in two classes, separating the relevant macro scale and micro scale indicators. Thus, the built environment factors are described in the first part of this section, followed by a characterization of pedestrian features that encourage walking. 

Neighbourhood macro scale

The literature review presented in this section describes the physical attributes of the environment that impact walkability. The urban features such as 5Ds: Density, Diversity, Design, Destination accessibility and Distance to transit (Ewing et al., 2009; Ewing and Cervero, 2010; Giles-Corti et al., 2016) are usually presented in the literature (Jeffrey et al., 2019).. Boulange et al. (2018) identified six (6) design characteristics, including residential density, land use mix, street connectivity, the proximity of destinations, presence of sidewalks, and access to public transport infrastructure (Adams et al., 2013). These design attributes affect physical activity and are considered to be constantly correlated with walking transport participation (Ainsworth, Barbara E and Caroline A, 2012). Schreuer et al. (2019) defined three main variables of the spatial layout of neighbourhoods that affect its walkability degree; (1) The land use compound, which is characterized by the disposition of shops, schools, workplaces, health and other public services. (2) Density; a high residential density generates a compact environment that enhances walkability. (3) The street pattern increases walkability by creating a high degree of connectivity and continuity when streets are in the grid network order. Besides, offering short and direct paths between the various destinations. The land-use diversity is a critical indicator to stimulate walking activity (Ewing and Cervero, 2010). The land-use defines a combination, such as commercial ground-floor façades, which has an important impact in attracting people at different times, including at night (Lamour et al., 2019). It is also known to foster the occupation and livability of the streets. Moreover, the proximity to a destination encourages people for selecting walking as the first mode of transport (Agrawal et al., 2008). Furthermore, land-use diversity improves a neighbourhood’s liveliness and generates a good quality of life (Burdett et al., 2005; Lamour et al., 2019) besides providing a secure community. Gehl et al. (2006) and Marcus and Francis (1997) highlight the necessity of diversity in the urban landscape because the visual dynamicity and crowded rhythm improve the urban walking experience. In contrast, endless walls and whole closing blocks transform the streets into monotonous and unsure urban spaces (Lamour et al., 2019). The high population density is usually associated with walkability in the literature (Lamour et al., 2019). It increases the efficiency of using infrastructure and enhances street life vivacity. However, it is considered an isolated attribute that is not up to improve walkability 14 (Jacobs, 2016). Therefore, it must be considered a critical feature in promoting walking indirectly (Lamour et al., 2019). The walkability is upgraded when multiple land uses are associated with residential areas (Schreuer et al., 2019). High street connectivity increased land use mix and increased residential density conduct to a high level of walkability (Frank et al., 2006). Alternatively, another study carried out by the London Planning Advisory Committee designed the multidimensional 5Cs plan (Gardner et al., 1996). Accordingly, a pedestrianfriendly environment must be: Connected, Convenient, Comfortable, Convivial and Conspicuous (Moura et al., 2017). Indeed, these characteristics emphasize the interaction between the built environment and walkability (Saelens and Handy, 2008). Table 1 shows the description of the 5Cs layout. Moura et al.(2017) proposed two extra factors emphasising the built environment’s major attractiveness-related amenities. These two factors are not mentioned in the existing 5Cs, such as (1) Coexistence related to pedestrian safety from traffic and the traffic effect on public space. (2) Commitment that includes the pedestrian politics development by local authorities (Table 1). 

Neighbourhood microscale

The micro-scale, or another term, the minor attributes of the environment, includes sidewalk quality and aesthetics (Cain et al., 2017). That can influence people’s comfort and safety during the walking experience in neighbourhoods (Cain et al., 2014; Sallis et al., 2015). The neighbourhood micro-scale characteristics have rarely been effectively studied (Cain et al., 2017). However, they should be measured to apprehend the all-inclusive dimensions of the sidewalk’s physical condition (Aghaabbasi et al., 2017). Many works on health and urban planning highlighted the positive correlation between high physical activity scores (walking) and sidewalks availability at the neighbourhood scale (Aghaabbasi et al., 2018; de Vries et al., 2007; Rodríguez et al., 2008). The micro-level approach at the neighbourhood scale, which can more easily account for frequent changes than at the macro level, has rarely been explored (Cain et al., 2017). Using the micro-scale approach can contribute to the provision of attractive sidewalks, pleasant and comfortable walking paths. Urban furniture such as drinking fountains (Cambra, 2012; Sarkar S., 2002), slope (Aghaabbasi et al., 2017; Akiyama and Kim, 2005a) and benches (Architectural and Board, 2004; Clifton et al., 2007) provide a comfortable environment for pedestrians in urban areas besides other social benefits (Jacobs, 1993; Lamour et al., 2019; Marcus and Francis, 1997). Walkability is also influenced by artificial shade’s visual quality and aesthetics (Kim et al., 2012; Laurentin et al., 2000) as well as natural shade. Indeed, vegetation has the aesthetic potential to create attractive spaces (Jacobs, 1993; Lamour et al., 2019). Trees that provide shade (Taleai and Taheri Amiri, 2017) encourage citizens to walk around the streets during the hot hours of the day (Lamour et al., 2019). The efficiency of vegetation associated 17 assessments such as green roofs and green walls (Lee and Jim, 2017).Which have been examined in improving biometeorological conditions (Lee et al., 2020). Moreover, this approach adds a safe dimension to the neighbourhood, for example, by implementing a speed limit for motorized vehicles (30 km/h) (Hamilton-Baillie, 2008) and appropriate signage for pedestrian crossing (Lamour et al., 2019). The quality of pavement is another parameter considering pedestrian safety, which must be spacious, without steps or obstacles, and good quality to assure security and comfort to all users (Gehl et al., 2006a). Accessible open spaces such as parks and squares have a crucial role regarding pedestrian activity, safety and comfort (Gehl et al., 2006a; Lamour et al., 2019; Marcus and Francis, 1997; Mateo-Babiano, 2016). Walkability micro-scale assessment models allow perceiving the walking environment better (Asadi-Shekari et al., 2019). That must be considered in designing walkable neighbourhoods (Schreuer et al., 2019).

Street scale

According to Aghaabbasi et al. (2019), sidewalks are the principal links to ensure walking (Hooker, 2007). They are crucial factors for promoting sustainable transportation (e.g., walking, cycling) (Aghaabbasi et al., 2017; Saito et al., 2013; Taboada, 2015). The street users include all categories (e.g., age, gender, physical condition). Accordingly, it is requisite to design sidewalks that are adequate with an extensive range of users (Aghaabbasi et al., 2017; Asadi-Shekari et al., 2013b). These primary channels should provide safe, healthy and all-inclusive walking conditions (Aghaabbasi et al., 2018). Sidewalk amenities conducive to comfortable walking involve main facilities (e.g., kerbs, ramps, sidewalk width), encouragement facilities (e.g., lighting, sitting areas, landscaping and trees) and convenience facilities (e.g., toilets, drinking fountains) (Asadi-Shekari et al., 2019). Such indicators can transform spaces into accessible, walkable and comfortable areas (Grahn and Stigsdotter, 2003; Ruiz-Padillo et al., 2018). Aghaabbasi et al. (2018) divided walkability indicators into different components, such as accessible design factors (e.g., accessible drinking fountains, accessible toilets, tactile pavements, kerb ramps, accessible signage and signals, skybridge lifts); safety design factors (e.g., landscaping and trees, signage, bollards, surfaces and materials, lighting, signals); attractiveness design factors (e.g., landscaping and trees, benches and sitting areas, rubbish bins, effective sidewalk width, lighting, cleanliness); and sidewalk path conditions (e.g., maintenance, slope, natural barriers). Other studies have used similar walkability indicators, such as seating areas, bollards, landscaping and trees, toilets, rubbish bins, skybridge lifts, driveways, slope, materials/surfaces, effective sidewalk width, signals, signage, tactile pavements, ramps, kerb ramps, cleanliness, lighting (Aghaabbasi et al., 2017), drinking fountains (Asadi-Shekari et al., 2019), shady trees, accessibility to green spaces, benches and pedestrian-scale lighting (AsadiShekari et al., 2014; Battista and Manaugh, 2018; Dixon, 1996; Grahn and Stigsdotter, 2003; Jensen, 2007). According to Asadi-Shekari et al. (2014), improvement in sidewalk conditions can be achieved by integrating certain walkability factors such as slower traffic, midblock crossing landscaping and trees, facilities (e.g., fire hydrants), lighting, signals, bollards, slope, kerb ramps, wheelchair-accessible drinking fountains, tactile pavements (warning and guiding), signals, benches and seating areas. Street lighting is essential to ensure security and safety (Loukaitou-Sideris, 2006). These walkability indicators are suitable for all users, including people with disabilities. It is also necessary to constantly measure existing sidewalks to verify their accommodation with all people needs considering socio-demographic properties, physical, sensory and cognitive conditions (Aghaabbasi et al., 2019, 2017; Asadi-Shekari et al., 2013b; Kadali and Vedagiri, 2016). Table 2 shows the street facilities and their impact on pedestrian comfort.