The climate change mitigation effects of daily active travel in cities

Abstract

Active travel (walking or cycling for transport) is considered the most sustainable form of personal transport. Yet its net effects on mobilityrelated CO 2 emissions are complex and under-researched. Here we collected travel activity data in seven European cities and derived life cycle CO 2 emissions across modes and purposes. Daily mobility-related life cycle CO 2 emissions were 3.2 kgCO 2 per person, with car travel contributing 70% and cycling 1%. Cyclists had 84% lower life cycle CO 2 emissions than non-cyclists. Life cycle CO 2 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 CO 2 emissions by 3.2 kgCO 2 /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.

Analyzing Spatiotemporal Daily Travel Source Carbon Emissions Based on Taxi Trajectory Data

“…Yang et al (2018) investigated travel emissions of the working class based on travel survey data and found that people producing high emissions were typically male with a high income that owned a car and were 30-40 years old [18]. Brand et al (2021) compared the impact of car travel and active travel (walking or cycling for transport) on travel emissions using travel activity data [35]. Calculating the residents' carbon emissions based on traditional travel surveys, questionnaires, or interviews is the principal means of bottom-up methods.…”

Active Travel’s Contribution to Climate Change Mitigation: Research Summary and Outlook

“…A notable exception is a recent study of daily travel behaviour (i.e. all trips recorded on a given weekday) of more than 3,500 participants across seven European cities, which found that 'cyclists' had 84 percent lower life cycle CO2 emissions from all daily travel than 'noncyclists' (Brand et al, 2021a). It also found that mobility-related life cycle CO2 emissions were 14% lower for those participants who cycled one trip/day more, and 62% lower for those who used a car or van for one trip/day less (while keeping everything else constant).…”

“…Many studies to date have focused on commuting. Life cycle CO2 emissions from social, shopping, personal business and recreational journeys have been shown to be more strongly associated to car use, and that shopping and personal business trips were found to be significantly shorter, therefore increasing the potential for mode shift to active travel (Brand et al, 2021a, Brand et al, 2014, Brand et al, 2021b. This suggests that future work should go beyond the commute and include all journey purposes.…”

“…Some people travel a lot, especially by motorized means, while others do not travel at all. A major European study found that the top 10% of survey participants were responsible for 59% of carbon emissions, and that those with better car access, higher incomes and poor bus accessibility producing higher emissions overall (Brand et al, 2021a). This is important for targeting mitigation efforts at the highest emitters while not increasing emissions of the lowest.…”

A paradox of traffic and extra cars in a city as a collective behaviour

“…Increasing active transport, such as walking or cycling, is proposed to address both health and environmental issues [ 1 – 4 ] and public transport provides a less polluting, low-cost and socially equitable travel alternative [ 5 ]. For every driver that switches to other transportation modes, such as walking, cycling or public transport, many daily kilos of CO 2 emissions are saved [ 6 ]. Yet, convincing drivers to switch to other transportation modes is a big challenge in most cities, where commuters are inclined to use a private car, imposing negative costs to the rest of the city, such as crashes and road injuries, congestion, air pollution, noise and the inefficient use of public space [ 7 , 8 ].…”