Active travel (walking or cycling for transport) is considered the most sustainable form of personal transport. Yet its net effects on mobility-related CO₂ emissions are complex and under-researched. Here we collected travel activity data in seven European cities and derived life cycle CO₂ emissions across modes and purposes. Daily mobility-related life cycle CO₂ emissions were 3.2 kgCO₂ per person, with car travel contributing 70% and cycling 1%. Cyclists had 84% lower life cycle CO₂ emissions than non-cyclists. Life cycle CO₂ emissions decreased by −14% per additional cycling trip and decreased by −62% for each avoided car trip. An average person who ‘shifted travel modes’ from car to bike decreased life cycle CO₂ emissions by 3.2 kgCO₂/day. Promoting active travel should be a cornerstone of strategies to meet net zero carbon targets, particularly in urban areas, while also improving public health and quality of urban life.

主动出行（步行或骑自行车出行）被认为是最可持续的个人交通工具。然而，其对与出行相关的CO ₂排放的净影响是复杂的，并且研​​究不足。在这里，我们收集了七个欧洲城市的旅行活动数据，并得出了不同模式和目的的生命周期CO ₂排放量。每天与出行相关的生命周期中，CO ₂排放量为每人3.2 kgCO ₂，其中汽车出行占70％，自行车出行占1％。与非骑自行车者相比，骑自行车者的生命周期CO ₂排放降低了84％。每增加一次骑车旅行，生命周期内的CO ₂排放量降低-14％，而每次避免的排放量则降低-62％汽车旅行。从汽车到自行车“将出行方式改变”的普通人将生命周期内的CO ₂排放量减少了3.2 kgCO ₂ /天。促进积极出行应该是实现零碳净目标的战略的基石，尤其是在城市地区，同时还应改善公共卫生和城市生活质量。