Heat and noise exposure during active travel: a systematic review

Exposure to heat and noise during active travel can offset some health benefits from walking and cycling as well as reduce travellers’ motivations to walk or bike. Most travel-based exposure studies focus on air pollution while neglecting heat and noise exposure. We systematically reviewed 94 empirical studies on heat and noise exposure during active travel and identified research gaps and future directions. We found that few studies have considered the bidirectional relationship between exposure and active travel. Most previous studies investigate the effects of active travel on exposure through simple designs with few designated travel routes or locations. They have identified a strong association between objective exposure and perception of exposure. However, little is known about how exposures affect active travel behaviour and human perception in actual travel. We identify research gaps such as the low space–time variability in exposure estimation and limited focus on different vulnerable groups. Few studies have focused on the combined effects of exposure to multiple environmental hazards and the effectiveness of mitigation strategies to reduce exposure. We also point out the need for studying the effects of exposure on travel behaviour and well-being. Overall, improved study designs – such as long-term mobility tracking of real-life active travel combined with high-resolution environmental data – could significantly enhance exposure assessment during active travel and better inform interventions for multiple exposure types.