Enabling heat-stress-resilient mobility with the HEAL navigation app in Germany

Key Learnings

About the Region

Climate Threats

Figure 1: Infrared image of the surface radiation temperature on a hot day in July 2022 on the ‘Promenade’ in Heidelberg’s ‘Bahnstadt’ district. Image Credit: Foshag et al. (2024).

From sensors to citizens: heat-adapted mobility in Heidelberg

Monitoring climate change and implementing appropriate heat adaptation measures in Heidelberg relies on climate assessments, sensors, and models.

In response to the emerging challenges associated with extreme heat, Heidelberg developed a Heat Action Plan (in German)  as an adaptation framework. It includes heat-stress prevention and adaptation measures, such as greening and de-sealing surfaces, providing drinking water points and shaded areas, and targeted information and protection for particularly at-risk groups. Innovative urban climate analyses and tools, such as the Climate Scanner (Klimascanner, in German), can support planning climate-friendly construction projects and maintain the quality of life for Heidelberg’s inhabitants. Other adaptation measures include promoting greening of facades and roofs, climate-smart urban development, and involving the public in preventive measures and self-help initiatives.

In line with these efforts, the HEAL (Heat Adaptation for Vulnerable Populations) project responds to the growing risks of urban heat stress. The measures within this project ensure safe mobility and support daily activities during heat events, primarily focusing on pedestrians, but also accommodating cyclists. The project complements the broader Heat Action Plan by providing innovative solutions.

Figure 2: A HEAL route in Heidelberg from the old town to the city library with two different options showing the heat stress along both paths. Image Credit: HEAL project.

Central to the project is a heat-stress-avoidant navigation App to help at-risk groups and others navigate the city more safely during periods of extreme heat. Using near-real-time sensor data, shadow modelling and input from at-risk groups collected in surveys, expert interviews, city walks, and informal exchanges, the navigation App calculates alternative routes that steer users away from heat-exposed main roads and instead guide them through shaded areas and parks. Additionally, it provides detailed information on path characteristics, including surface type, gradient, and overall walkability, ensuring accessibility for different user groups. To further refine the routing approach, the project team simulated 10,000 pedestrian trips in Heidelberg at different times of the day to analyse variations in route selection based on heat exposure. These simulations helped optimise the algorithm.

Figure 3: Together with the target groups researchers developed individual adaptation strategies and protective measures to enable everyday life and mobility even during hot days. Photo: Kathrin Foshag.

Beyond aiding mobility, the project measures include raising awareness about climate change and the impact of heat stress in urban environments. A key component of HEAL is its transdisciplinary approach, which actively involves local stakeholders such as the Office for Environmental Protection, the Academy for Older People and senior and family community/network members. To ensure the navigation App addresses real-life challenges and is easy to use, the project team organised five interactive city walks, surveys, interviews (mobile and static), participatory and mental mapping. Those engagement activities allowed at-risk groups to highlight specific mobility challenges, share their heat-avoidance strategies, and identify critical problem areas. A heat workshop at the Bahnstadt district engaged pupils from a secondary school in discussions on heat-related health risks and potential solutions. These methods provided insights beyond numerical data, revealing how different groups experience heat stress, which areas in Heidelberg are perceived as heat hotspots and how a routing application can be designed to be more accessible, particularly for the elderly population.

Interdisciplinarity connects experts across fields like geography, computer science, medicine, and the social sciences; transdisciplinarity goes a step further, bridging science with society and practice. To develop practical and effective solutions, it is essential to engage directly with the target groups.

Dr. Kathrin Foshag, Senior Researcher at TdLab Geography, Heidelberg University.

Figure 4: A HEAL route in Worms from the main train station to the Rhine promenade: slightly different routes are suggested in the morning and afternoon to avoid heat stress. Image Credit: HEAL project.

The HEAL team has successfully launched the navigation App in Heidelberg during the summer of 2024. The project design allows for transferring the overall approach and the App to other German cities, extending the benefits beyond Heidelberg. Thanks to close collaboration with the municipality of Worms and Walldorf, the app is now also available for these urban areas. Looking ahead, the HEAL team aims to further expand the app’s availability to embed climate adaptation strategies into urban infrastructure across Europe.

HEAL aligns closely with our heat network approach in Worms. It is a tool that can be used by multipliers and decision-makers as well as directly by affected groups. Our next aim is to explore how HEAL can support the planning of future heat adaptation measures.

Marco Elischer, Climate Protection Manager for the City of Worms.

Figure 5: Marco Elischer, Climate Protection Manager for the City of Worms, presenting the HEAL app as part of the Ready4Heat project and Cities Refresh Campaign. Image Credit: Alicia Göpner / Climate Alliance.

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