Background <p>Active transport can increase physical activity at the population level, thereby improving population health. Knowing the health and related economic benefits of infrastructure measures that change physical activity may help underpin the case for investment, but valuing such benefits is challenging.</p> Objective <p>The aim of this study was to develop a model to estimate the health benefits of changes in active transport behaviour and translate these to an economic value. We applied the model to the state of New South Wales, Australia.</p> Methods <p>The The Active Transport Health Model is a proportional multi-state lifetable model that quantifies the health impacts of changes in active transport behaviour over a population’s lifetime. Health outcomes related to physical activity, air pollution and road trauma are modelled. Model outputs include age- and sex-specific changes in disease incidence, prevalence and mortality, summarised as health-adjusted life-years, which are translated to monetary terms. Changes in healthcare costs are also modelled. Values per additional person-kilometres of walking and cycling are reported (in Australian dollars). A 5% discount rate is applied.</p> Results <p>Compared to car use, the health benefits for an additional person-kilometre walked are AU$4.41 (95% uncertainty interval AU$3.81–AU$5.05), and AU$2.42 (95% uncertainty interval AU$2.05–AU$2.76) for an additional person-kilometre cycled. This varies with various factors such as age and current physical activity level.</p> Conclusions <p>The Active Transport Health Model can be used to assess and value the health benefits of active transport. The monetary per-kilometre values in our study were higher than those of previous studies. This has important implications for infrastructure planning and guidelines on transport projects where monetised health benefits of physical activity are factored into cost-benefit analyses.</p>