Background The EU has set the most ambitious greenhouse gas emissions reduction targets in the world, with binding mechanisms already in place that guarantee a unilateral 20% reduction by 2020 compared to 1990 levels. The EU is committed to increase this figure to 30% in 2030. Member States must promote policies that will result in the prevention of climate change, and several industrial sectors have been required to measure their carbon footprints – usually reported as greenhouse gas (GHG) emissions in CO2 equivalents. Air quality thresholds for particulate matter, ground-level ozone and nitrogen dioxide are foreseen by the Air Quality Directive – but these thresholds are exceeded in the most densely populated areas. The Roadmap for a Resource Efficient Europe (2011) reported that a better implementation of existing legislation in combination with new science-based standards for air quality and the transition to a low-carbon economy would benefit air quality. Objectives The main objective of the LIFE GYM project is to contribute towards reducing EU GHG by introducing a sustainable mobility strategy and by promoting environmentally optimal co-modal options for commuting and travelling. Specific project objectives are to: Develop tools that will accurately measure the emissions of public vehicles circulating in the EU public transport networks under consideration; Develop tools that will identify the most environmentally friendly journey from any point of the network under consideration (at least Czech, Dutch and Greek locations) to another by using public transport and optimising passenger logistics; Develop, demonstrate and promote an integrated platform that will lead to the decrease of GHG emission production and energy consumption (per kilometre travelled, per passenger) in the European transport sector by reducing the demand for travel by car, making public transport greener, more efficient, accessible and attractive; Change the culture and the commuting habits of passengers by providing an easy-to-use service while raising awareness of the environmental benefits; Decrease the CO2 -equivalent per passenger and kilometre; Introduce an innovative policy in the pan-European transport system, based on the efficient co-modality scheme and EU emission regulations; Raise awareness and mobilise key local, regional and national actors in order to adopt environmental measures towards sustainable urban mobility; and Support networking and exchange of practices at transnational level with the target of environmental integration in policy areas related to transport. Expected results: An open database covering 70% of the Greek public transport network for the first time; Novel co-modal energy consumption and GHG emission calculation models for European public transport means; An improved modelling and solution approach for the environmental co-modal vehicle routing problem, which is the basis for energy-efficient sustainable transport; Demonstration of the first national co-modal environmental public transport planner in Greece in 16 major cities and of a pan-European journey planner service via a web platform and a smart phone application replicated in at least four journey planners in EU countries (Czech Republic, The Netherlands, Romania, Slovakia); Improved results and higher accuracy of the COPERT emission calculation software coordinated by the European Environment Agency (EEA) via the adoption of GYM models; Change the culture of the commuters and encourage them to shift their habits from using the car to using the public transport by promoting co-modal and environmentally efficient transport patterns; Reduction of air pollution and emissions in cities: reduction of at least 2 699 Mt CO2 eq. during the lifetime of the project; Introduction of an integrated policy for sustainable urban mobility based on the efficient co-modality scheme and EU emission regulations in at least five countries via five journey planners within the funded period; and Door-to-door urban mobility by creating the framework conditions and a strong mechanism of cooperation between stakeholders of different administrative levels and transport operators.