Can the enhanced mobility created by transportation infrastructure investments help people to avoid environmental extremes? We use transaction records from China’s card payment system to measure experienced pollution exposure (EPE) - that is, exposure based on the pollution levels at travelers’ actual locations - and evaluate how EPE was affected by the country’s high-speed railway network, even while holding pollution itself constant. Our estimates imply a reduction in EPE that corresponds to a mortality benefit of 21.3 million life-years saved, primarily due to travelers changing their destinations towards locations with predictably cleaner air.