Individual and city-level variations in heat-related road traffic deaths in Latin America

Road-traffic mortality and extreme heat are two major urban health challenges, increasingly found to be associated. However, few studies have examined this association in Latin America-one of the world's most urbanized, fastest-motorizing region, with a high share of vulnerable road users-and even fewer have analyzed multiple cities across diverse climates and urban settings. Using temperature and road-traffic mortality data (2000-2019) from 272 cities in six Latin American countries, we conducted a time-stratified case-crossover study. The relative risks (RRs) of road-traffic mortality at the 95th and 99th temperature percentiles, compared to the minimum mortality temperature percentile, were 1.16 [95% CI: 1.14-1.19] and 1.18 [1.15-1.21], respectively. Risks were particularly high among adolescents, males, motorcyclists, bicyclists, and in cities with hotter climates and longer commutes. Policymakers in the tropical Global South should prioritize protecting vulnerable road users in peripheral communities, where many endure long, heat-exposed commutes in non-climate-controlled informal transport.