Active travel (walking or cycling for transport) is considered the most sustainable and low carbon form of getting from A to B. Yet the net effects of changes in active travel on changes in mobility-related CO₂ emissions are complex and under-researched. Here we collected longitudinal data on daily travel behavior, journey purpose, as well as personal and geospatial characteristics in seven European cities and derived mobility-related lifecycle CO₂ emissions over time and space. Statistical modelling of longitudinal panel (n = 1849) data was performed to assess how changes in active travel, the ‘main mode’ of daily travel, and cycling frequency influenced changes in mobility-related lifecycle CO₂ emissions.

We found that changes in active travel have significant lifecycle carbon emissions benefits, even in European urban contexts with already high walking and cycling shares. An increase in cycling or walking consistently and independently decreased mobility-related lifecycle CO₂ emissions, suggesting that active travel substituted for motorized travel – i.e. the increase was not just additional (induced) travel over and above motorized travel. To illustrate this, an average person cycling 1 trip/day more and driving 1 trip/day less for 200 days a year would decrease mobility-related lifecycle CO₂ emissions by about 0.5 tonnes over a year, representing a substantial share of average per capita CO₂ emissions from transport. The largest benefits from shifts from car to active travel were for business purposes, followed by social and recreational trips, and commuting to work or place of education. Changes to commuting emissions were more pronounced for those who were younger, lived closer to work and further to a public transport station.

Even if not all car trips could be substituted by active travel the potential for decreasing emissions is considerable and significant. The study gives policy and practice the empirical evidence needed to assess climate change mitigation impacts of urban transport measures and interventions aimed at mode shift to more sustainable modes of transport. Investing in and promoting active travel whilst ‘demoting’ private car ownership and use should be a cornerstone of strategies to meet ‘net zero’ carbon targets, particularly in urban areas, while also reducing inequalities and improving public health and quality of urban life in a post-COVID-19 world.

主动出行（步行或骑自行车出行）被认为是从A到B的最可持续且低碳的形式。然而，主动出行的变化对与出行相关的CO ₂排放变化的净影响是复杂的，并且研​​究不足。在这里，我们收集了有关七个欧洲城市的日常出行行为，出行目的以及个人和地理空间特征的纵向数据，以及随时间和空间而得出的与移动性相关的生命周期CO ₂排放量。进行了纵向面板（n = 1849）数据的统计建模，以评估主动出行的变化，每日出行的“主要模式”以及骑自行车的频率如何影响与出行相关的生命周期CO ₂排放的变化。

我们发现，即使在步行和骑车比例已经很高的欧洲城市环境中，主动出行的变化也可以显着提高生命周期的碳排放量。持续增加骑行或步行的次数并独立地减少了与机动性相关的生命周期中的CO ₂排放，这表明主动出行代替了机动出行–即，增加的不仅仅是在机动出行之外的额外（诱导）出行。为了说明这一点，一个普通人每年增加200次骑行每天1次旅行和每天减少骑行1天每天，一年内将减少与机动性相关的生命周期CO ₂排放量约0.5吨，占人均平均排放量的很大一部分一氧化碳₂运输产生的排放。从汽车旅行到主动旅行的最大好处是出于商务目的，其次是社交和休闲旅行，以及通勤去上班或上学的地方。通勤排放的变化对于那些年轻，居住在离工作地点更近，更靠近公共交通站点的人来说更为明显。

即使不是所有的出行都可以由主动出行代替，减少排放的潜力仍然是巨大而显着的。该研究为政策和实践提供了经验证据，以评估城市交通措施和干预措施的气候变化缓解影响，这些措施和干预旨在实现模式向更可持续的交通方式的转变。在“降低”私家车拥有量和使用量的同时，投资和促进积极出行应成为实现“零碳”碳目标（尤其是在城市地区）的战略的基石，同时还应减少不平等现象并改善公共健康和城市生活质量。后COVID-19世界。