New App Maps Shadiest Walking Routes to Combat Extreme Heat

A new application developed by Arizona State University (ASU) researchers aims to help people navigate urban environments by identifying the shadiest walking routes. The “Cool Routes” app is designed to combat the dangers of extreme heat, particularly in arid regions, by factoring in a more comprehensive measure of heat exposure than simple air temperature.

Understanding Heat Load

The app, created by Ariane Middel and her colleagues at ASU’s SHaDE Lab, calculates routes based on forecasted mean radiant temperature. This metric accounts for the total heat load a person experiences, which includes not only direct sunlight but also reflected heat from surfaces like buildings and pavement. This is a critical distinction in cities where direct sun can dramatically increase perceived temperatures.

In Phoenix, Arizona, for example, mean radiant temperature in full sun can exceed 150 degrees Fahrenheit, while shaded areas might see temperatures below 100 degrees Fahrenheit. The app’s creators highlight that shade can significantly reduce a person’s heat exposure on hot, sunny days, making a tangible difference to comfort and safety.

Functionality and Potential

The Cool Routes app updates hourly with the latest weather data, providing real-time guidance. During testing, the app successfully identified cooler alternative routes for 70% of tested journeys. On average, these shaded paths reduced the experienced heat load by approximately 4.5 degrees Fahrenheit.

While the current version of the app focuses on ASU’s Tempe campus, it is built on an open-source framework. This design allows for its adaptation and implementation in other cities worldwide. The researchers envision the app supporting various modes of transport, including walking, cycling, and public transit use, by making these options more appealing and safer during hot weather.

The development of such tools is increasingly important as urban areas grapple with rising temperatures and the intensification of heatwaves, a phenomenon linked to climate change. Providing residents with practical ways to avoid the most intense heat exposure can be a crucial public health measure, especially for vulnerable populations.

Adapting for London

While the Cool Routes app originated in Arizona, its underlying principles have relevance for London. As the UK capital experiences more frequent and intense heatwaves, understanding and mitigating urban heat island effects is becoming a priority. The concept of mapping shade, beyond just air temperature, could inform urban planning decisions. This includes the strategic planting of trees, the design of public spaces to maximise shaded areas, and the orientation of new developments.

The success of the Cool Routes app in identifying cooler paths highlights the potential for similar technology to influence pedestrian navigation apps and public transport information systems in London. By integrating shade data, these platforms could offer users route options that prioritise thermal comfort, thereby encouraging active travel even during hot periods.

Challenges and Future Development

The expansion of the Cool Routes framework to other cities will depend on the availability of detailed local data, including high-resolution weather forecasts and detailed urban morphology that captures building heights, street widths, and the presence of vegetation. The open-source nature of the project, however, suggests that collaboration and community input could drive its future development.

For London, incorporating such a tool would require collaboration between meteorological services, urban planning departments, and transport authorities. The data gathered could also be invaluable for long-term urban resilience strategies, helping to identify “heat hot spots” within the city and guiding interventions aimed at increasing green infrastructure and shaded public spaces.

The implications extend beyond individual navigation. City planners could use data generated by such applications to identify areas lacking adequate shade and prioritise greening initiatives or streetscape improvements. This data-driven approach can complement existing efforts to make London more resilient to the impacts of climate change, ensuring that the city remains a liveable and comfortable environment for all its residents.

Key facts

Source: Planetizen News (https://www.planetizen.com/news/2026/06/137813-cool-routes-app-plots-shady-walks-arid-arizona)