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Enhancing Microclimate of Non-motorized Transportation Environments

Description:

Urbanization has continuously jeopardized natural and built environments by letting the demand for land use change increased rapidly. At the community level, supporting human activities in urban areas consumes enormous energy support systems (such as cooling in buildings and running transportation) emitting a lot of waste heat into the air, which accelerates urban heat islands effect (UHI). Meanwhile, when solar radiation meets artificially covered or paved surfaces such as urban streets, bike lanes, and trails, they are heated and give unfavorable influences on human activities (Oke, 1982; Barzyk and Frederick, 2006).

Complete Streets policies have summarized that many US communities would have improved the quality of their street environments to be safe and convenient to use. However, rapid climate change and the quality of streetscapes to promote non-motorized transportation environments such as walking and bicycling have not been fully investigated. Especially in summer, UHI affects urban street conditions to increase heat-related health risks for people with lack of design considerations to cool down urban streetscapes. Some population groups such as elderly or adolescents can be more vulnerable to the heat wave and to experiencing heat stress, heat stroke, and insufficient sleep (O’Loughlin et al., 2012; Zhou et al., 2014; Jacklitsch et al., 2016). The matters are due to highly increased air temperature caused by excessive heat from pathways, roads, and vehicles (Oke, 1982; Barzyk and Frederick, 2006). UHI mitigation studies have reported various mitigation strategies (Lindberg and Grimmond, 2011; Asgarian et al., 2014; Coutts et al., 2015; Park et al., 2017). As one of the temperature mitigation strategies, the use of urban green spaces is well documented to create cooling zones in urban areas (Taha et al., 1991; Dimoudi and Nikolopoulou, 2003; Zoulia et al., 2009). They shade urban paved areas against direct solar radiation and provide surrounding areas with humidity resulting in the air temperature decreases (Oliveira et al., 2011; Kim et al., 2016). Those green spaces provide people cooling streets, bike lanes, and trails and reduce heat-related human damages (Georgi and Dimitriou, 2010; Ng et al., 2012). However, there are only a few researchers that have investigated cooling strategies on a fine scale assessing the cooling effects of green space and creating a pleasant street to provide thermal comfort.

Objective:

A number of communities have developed their resilience plans to adapt to heat, flood, sea level rise and so on. Heat reduction strategies in urban streets are commonly found in resilience plans. These plans may just begin to recognize the significance of excessive heat and heat-related damages and the importance of cooling strategies. To succeed in heat mitigation with cooling design practices, we should optimize design strategies to identify which part of the street segments could maximize cooling effects with green spaces. For example, the cooling street design with green spaces should consider their optimal sizes, volumes and configurations where street green spaces should be. These design strategies help to create a guideline for cooling transportation environments. However, those guidelines have not been documented well and supported by many urban studies.

The issue is mainly due to the difficulty to capture precise spatial data of microclimate on a fine scale to assess the contribution of green spaces. Moreover, how to collect microclimate data at street level has not been fully demonstrated yet due to the limitations of measurements using less accurate monitoring devices. Utilizing temperature-sensing unit ventilated with double cylinder shelters (TVCs) will be capable of collecting much precise and reliable temperature data by measuring air temperature and introducing an advanced transect survey method which deals with more detailed data.

The overall purpose of this research is to establish a cooling street design guideline for community resiliency on a fine scale to mitigate urban heat on urban streets. The study is also to assess how to collect the air temperature data at a street level with TVCs and how we improve streetscape design to offer cooling transportation environments. Specific aims of this study are as follows:

  1. to develop a measurement method using TVCs to detect air temperature on various non-motorized transportation environment types.

  2. to compare microclimates of urban streets representing various physical environments mainly focusing on exposed areas to solar radiation and shaded areas with green spaces.

  3. to establish a cooling street design guideline to improve non-motorized transportation environments using urban green spaces.
Related Research:

1. Green spaces reduce UHI through their cooling features.

  1. Sensing the microclimate of green spaces needs more accurate devices and methods.
Relevance:

The outcomes of this research will help researchers, planners, engineers and policy makers conduct Complete Street projects and improve their communities' resiliency. The findings of this study will contribute to creating healthier transportation environments by helping stakeholders choose the most appropriate types, structures, and arrangements of green spaces along with the streetscape required to optimize cooling. In addition, this study will inform them regarding how these green spaces should be designed and distributed to improve thermal comforts of pedestrians and bikers. The findings about disposition of green spaces can be applied to urban floods mitigation with more effective stormwater management design, because optimized-size and configurations of street green spaces will contribute to increase infiltration, and decrease runoff volume and time. This study will also help to develop more advanced measurement tools and protocols to collect microclimate data focusing on air temperature in various land-cover types; to develop thermal maps indicating the thresholds of positive impacts of green spaces.

Sponsoring Committee:AFB40, Landscape and Environmental Design
Research Period:24 - 36 months
Research Priority:Medium
RNS Developer:Jonghoon Park and Jun-Hyun Kim
Date Posted:09/16/2019
Date Modified:11/11/2019
Index Terms:Environmental design, Nonmotorized transportation, Temperature, Atmospheric temperature, Climate, Urban design,
Cosponsoring Committees: 
Subjects    
Pedestrians and Bicyclists
Planning and Forecasting
Research
Environment

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