BACKGROUND: By 2050, almost 70% of people globally are projected to live in urban areas. As the environments we inhabit affect our health, urban and transport designs that promote healthy living are needed. OBJECTIVE: We estimated the number of premature deaths preventable under compliance with international exposure recommendations for physical activity (PA), air pollution, noise, heat, and access to green spaces. METHODS: We developed and applied the Urban and TranspOrt Planning Health Impact Assessment (UTOPHIA) tool to Barcelona. Exposure estimates and mortality data were available for 1357361 residents. We compared recommended with current exposure levels. We quantified the associations between exposures and mortality and calculated population attributable fractions to estimate the number of premature deaths preventable. We also modeled life-expectancy and economic impacts. RESULTS: We estimated that annually almost 20% of mortality could be prevented if international recommendations for performance of PA, exposure to air pollution, noise, heat, and access to green space were complied with. Estimations showed that the biggest share in preventable deaths was attributable to increases in PA, followed by exposure reductions in air pollution, traffic noise and heat. Access to green spaces had smaller effects on mortality. Compliance was estimated to increase the average life expectancy by 360 (95% CI: 219, 493) days and result in economic savings of 9.3 (95% CI: 4.9; 13.2) billion euro per year. CONCLUSIONS: PA factors and environmental exposures can be modified by changes in urban and transport planning. We emphasize the need for (1) the reduction of motorized traffic through the promotion of active and public transport and (2) the provision of green infrastructure, which are both suggested to provide PA opportunities and mitigation of air pollution, noise, and heat.