NTUA Professor George Yannis, after more than 30 years of dedication to road safety science and several Marathon races, decided to combine both passions for a cause: to run 30 Marathons in 30 months in order to actively promote the adoption of 30km/h speed limit in as many cities as possible worldwide, as a fundamental policy for safer, healthier and greener cities for all. Speeding is the number one cause of road crashes worldwide and the active promotion of 30 km/h cities can save 50% of lives lost today.