The hidden cost of heatwaves: empty high streets and unequal choices

As extreme heat becomes more frequent, the poorest workers cannot afford to stay home, while wealthier residents cut back on travel and social mixing declines

A study tracking 13 million people across Spain has uncovered inequalities in how different groups respond to extreme heat, with the poorest residents continuing to commute and work, while wealthier populations cut back on travel and discretionary activities.

The research analysed mobile phone data from 27% of Spain’s population across 2022 and 2023, matching movement patterns with high-resolution thermal comfort data.

It found on days when the Universal Thermal Climate Index (a measurement that aims to represent how the human body actually feels in outdoor conditions, rather than simply measuring the air temperature) exceeded 45°C.

Overall, mobility fell by up to 10%, and by as much as 20% in afternoons when temperatures peak.

The most significant findings, however, relate to social division. While older adults – the group most medically vulnerable to heat – reduced travel to work and other activities by up to 8% on the hottest days, individuals from the lowest income brackets showed almost no change in work-related travel. Wealthier residents, by contrast, cut non-essential trips by up to 15% when temperatures surpassed 45°C.

The researchers interpret this as the poor being unable to afford to miss work or lacking the option to work from home, while the wealthy can adapt by staying indoors or shifting to air-conditioned environments. 

Short trips of less than 2km, those most likely to involve walking or cycling, saw the largest declines, consistent with evidence that active travel is disproportionately abandoned during heatwaves. Longer journeys, more likely to involve air-conditioned vehicles, proved more resilient.

The study also revealed that on hot days, the normal pattern of trips flowing from less populous to more populous areas, and from lower-income to higher-income districts, broke down.

Social mixing declined, with fewer interactions between different economic groups. Significantly, it was the city centres that lost the most activity.

With cities in the UK also facing rising summer temperatures, strategies that rely solely on air conditioning and home working may preserve individual health but at the cost of street-level interactions that sustain city centres.

The research suggests that passive cooling interventions such greening, shading, reflective materials, may be essential not just for public health but for preserving the economic vibrancy of urban cores. 

The full research can be read here.

Photo: Soly Moses

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