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Reflective streets: Sunblock for streets

Asphalt is getting a makeover as reflective streets cool down cities and redefine urban infrastructure.

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Quantumrun Foresight
July 23, 2024

Insight summary

Reflective pavement technology offers a cost-effective solution to combat urban heat by applying special street coatings to reflect solar energy and lower surface temperatures. Despite showing promise in lowering ground temperatures, the effectiveness of reflective pavements varies based on urban configurations and time of day. While this innovation presents an opportunity to alleviate urban heat, its implementation requires careful consideration of urban design, climate, and pedestrian usage to avoid unintended consequences.

Reflective streets context

Reflective pavement technology is emerging as a compelling strategy for mitigating urban heat, particularly in car-centric cities with extensive road and parking lot surfaces. This approach involves applying a special coating to streets that reflects more solar energy into the atmosphere, thus reducing the surface temperature. In US locales like Phoenix, Arizona, and Los Angeles, California, initiatives to coat urban streets with reflective materials have shown promising results in lowering ground temperatures, although the impact on air temperature (Tair) and mean radiant temperature (Tmrt) varies depending on the time of day and specific urban configurations. For instance, in Phoenix, studies have demonstrated a notable reduction in surface temperatures in treated neighborhoods, highlighting the potential of reflective pavements to alleviate some of the heat absorbed and re-radiated by traditional asphalt.

The application of reflective pavements, however, requires careful consideration of urban design, climate, and the intended use of the space. According to a 2023 Nature study, it is most beneficial in areas with low cloud cover and extensive road networks, where the absence of shading structures allows for maximum reflection of solar radiation. Yet, in dense urban areas or "urban canyons" where high-rise buildings dominate, the effectiveness of reflective pavements diminishes due to the limited direct sunlight reaching the streets. Furthermore, the technology is not recommended for areas with high daytime pedestrian traffic, such as playgrounds and plazas, due to the potential increase in heat load on the human body.

As cities grapple with climate change challenges and urban heat islands, reflective pavement presents an innovative, albeit complex, solution. It offers a relatively affordable alternative to conventional air conditioning for urban areas and could extend pavement lifespan. Future research is essential to optimize the material composition of reflective pavements, assess their long-term durability, and understand their impact on surrounding vegetation and buildings.

Disruptive impact

In cities where these technologies are implemented, residents may find relief from urban heat, leading to more comfortable outdoor activities and potentially reducing heat-related illnesses. However, there's a risk that areas with high pedestrian traffic could experience increased heat stress due to the reflection of solar radiation. As a result, people may need to adjust their routines, avoiding certain areas during peak heat hours or adopting protective clothing and gear to mitigate the effects of increased radiant heat.

Businesses operating in urban areas might see changes in operational costs and consumer behavior due to reflective streets. Reduced ambient temperatures can lead to lower air conditioning expenses, saving companies money during hot months. However, businesses like cafes and retail stores with outdoor spaces may need additional shading solutions to keep customers comfortable against the reflective glare. Moreover, companies specializing in construction materials and urban planning services may find new opportunities to develop and implement reflective pavement technologies.

Municipalities may benefit from reduced energy expenditures and improved public health outcomes, making cities more livable and potentially attracting more residents and businesses. Globally, adopting reflective pavement technologies contributes to global efforts to combat climate change by reducing the urban heat island effect, aligning with environmental sustainability goals. However, governments may also need to consider the social and ecological trade-offs, ensuring equitable access to these benefits and addressing unintended consequences, such as impacts on local wildlife or increased cooling demands in adjacent buildings.

Implications of reflective streets

Wider implications of reflective streets may include:

A shift in urban planning priorities, focusing more on sustainable and heat-reducing infrastructure, leading to cooler, more livable cities.

Increased demand for reflective materials stimulating growth in the construction and materials industries, creating new jobs and business opportunities.

Local governments implementing tax incentives for property owners who adopt reflective surfaces, encouraging widespread adoption.

A rise in public health campaigns aimed at educating citizens on the benefits of cooler urban environments and how to safely navigate them.

Environmental policies incorporating urban cooling strategies as a standard part of climate adaptation measures.

Valuation increase for properties in areas with heat mitigation measures, affecting buyer preferences.

Schools and educational institutions adjusting their outdoor activity schedules or infrastructure to protect students from heat effects.

A decrease in energy consumption for cooling needs in urban areas, contributing to national efforts to lower carbon emissions.

Communities in hotter climates experiencing demographic shifts as they become more attractive places to live due to improved thermal comfort.

Urban wildlife and ecosystems facing stress or adaptation challenges due to altered microclimates from widespread implementation of reflective surfaces.