# Abstract We used Comparative Risk Assessment methods to estimate the health effects of alternative urban land transport scenarios for two settings—London, UK, and Delhi, India. For each setting, we compared a business-as-usual 2030 projection (without policies for reduction of greenhouse gases) with alternative scenarios—lower-carbon-emission motor vehicles, increased active travel, and a combination of the two. We developed separate models that linked transport scenarios with physical activity, air pollution, and risk of road traffic injury. In both cities, we noted that reduction in carbon dioxide emissions through an increase in active travel and less use of motor vehicles had larger health benefits per million population (7332 disability-adjusted life-years [DALYs] in London, and 12 516 in Delhi in 1 year) than from the increased use of lower-emission motor vehicles (160 DALYs in London, and 1696 in Delhi). However, combination of active travel and lower-emission motor vehicles would give the largest benefits (7439 DALYs in London, 12 995 in Delhi), notably from a reduction in the number of years of life lost from ischaemic heart disease (10–19% in London, 11–25% in Delhi). Although uncertainties remain, climate change mitigation in transport should benefit public health substantially. Policies to increase the acceptability, appeal, and safety of active urban travel, and discourage travel in private motor vehicles would provide larger health benefits than would policies that focus solely on lower-emission motor vehicles. # Key messages - Transport-related greenhouse-gas emissions are increasing, with a rapid growth projection in low-income and middle-income countries - Production of lower-emission motor vehicles (cars, motorcycles, and trucks) and reduction in travel by motor vehicles are needed to meet targets for reduction of greenhouse-gas emissions. - Lower-emission motor vehicles would reduce the health burden from urban outdoor air pollution, but a reduction in the distance travelled by motor vehicles could have a greater effect. - Increase in the distances walked and cycled would also lead to large health benefits. Largest health gains would be from reductions in the prevalence of ischaemic heart disease, cerebrovascular disease, depression, dementia, and diabetes. - Although reducing motor vehicle use would decrease the injury risk for existing pedestrians and cyclists, if many more people walked and cycled there might be an increase in the number of pedestrian and cycle injuries, since more people would be exposed to the remaining risk. - Creation of safe urban environments for mass active travel will require prioritisation of the needs of pedestrians and cyclists over those of motorists. Walking or cycling should become the most direct, convenient, and pleasant option for most urban trips. # Notes ## Implications for policy Effective policies to increase the distances walked and cycled and reduce use of motor vehicles are needed to achieve the health benefits we have discussed. Policies that encourage people to walk and cycle would be expected to increase the safety of active travel, as shown in our sensitivity analysis of injury risks in the Netherlands. Substantial increases in the distances cycled in cities, including Copenhagen (Denmark), London, and New York (USA), are associated with a decrease in the numbers of cyclists killed or seriously injured (webappendix p 38). ==Without strong policies to increase the acceptability, appeal, and safety of walking and cycling, the vicious circle of increased motorisation and road danger will continue in Delhi, and the large potential health and environmental gains will not be achieved.== Creation of safe urban environments for mass active travel will mean prioritisation of the needs of pedestrians and cyclists compared with those of motorists. Walking or cycling should be the most direct, convenient, and pleasant options for most urban trips. Policy makers should divert investment from roads for motorists towards provision of infrastructure for pedestrians and cyclists. Compared with cars and trucks, pedestrians and cyclists should have direct routes with priority at junctions. Strict controls for HGVs in urban areas are key safety prerequisites for cyclists. Properly enforced reductions in speed limits or zones can reduce injuries. With such policies, achievement of low levels of risk from road injury for active travel, at least as low as the best practice in the Netherlands, should be possible. Enhanced streetscape design can make active travel pleasant. With short distances, active travel becomes convenient; planned mixed-use developments would reduce distances to employment, education, services, and retail. [[Urban design matters|Urban form matters]] since the incidence of road traffic injuries and urban crime are related to street design and land-use patterns. Hence effective urban design can enable high modes shares for walking and cycling.