The climate change mitigation impacts of active travel: Evidence from a longitudinal panel study in seven European cities

Abstract Active travel (walking or cycling for transport) is generally good for health, the environment and the economy. 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, mode choice, as well as personal and geospatial characteristics in seven European cities and derived mobility-related lifecycle CO2 emissions from daily travel activity over time and space. Fixed- and mixed-effects modelling of longitudinal panel data (n=1849) was performed to assess the associations between changes in lifecycle CO2 emissions and changes in transport mode use (primary exposure), main mode of travel, and cycling frequency (secondary exposures). Daily mobility-related lifecycle CO2 emissions were 2.8 kgCO2 per person at baseline, with car travel contributing 69% and cycling 1%. At follow-up, mobility-related lifecycle CO2 emissions were -0.52 (95%CI -0.82 to -0.21) kgCO2/day lower per additional cycling trip, -0.41 (95%CI -0.69 to -0.12) kgCO2/day lower per additional walking trip, and -2.11 (95%CI -1.78 to -2.43) kgCO2/day lower per ‘avoided’ car trip. 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. Those who changed from ‘not cycling’ to ‘cycling’ decreased daily CO2 emissions by -2.54 (95%CI -3.90 to -1.17) kgCO2/day. Mobility-related CO2 emissions decreased by -9.28 (95%CI -11.46 to -7.11) kg/day for those who changed their ‘main mode’ from car, van or motorbike to active travel. Extensive sensitivity analyses by city, journey purpose and key personal characteristics largely confirmed our results. Active travel is shown to substitute for motorized travel, with significant climate change mitigation effects. Even if not all car trips could be substituted by active travel the potential for decreasing emissions is considerable and significant. Investing in and promoting active travel should therefore 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.