Walking and cycling to work is a natural way of increasing lifestyle activity in working population. In Finland, active travel is acknowledged as one of the key components in the most previous policy documents and initiatives related to physical activity promotion. However, the evidence on the effectiveness and cost savings of environmental as well as social and behavioral strategies in promoting active travel is thin both nationally and internationally. This study focuses directly on this gap by 1) conducting a cluster-randomized, controlled intervention where environmental change is supported with social and behavioral strategies in a large workplace area in Tampere, Finland, 2) assessing the cost-effectiveness and health-economic impact of the intervention and 3) examining the environmental mediators and moderators of active commuting to work among working aged population.