An NTUA Diploma Thesis called “Analysis of the acceptance and cost benefit analysis of reducing the speed limit to 80 km/h on the interurban road network in Greece” was recently presented by Konstantinos Makrydakis. For the purpose of this Diploma Thesis, a special questionnaire was developed and answered by 408 travellers, from different parts of Greece, based on the stated preference method for 10 hypothetical scenarios with variations of the variables travel time, fuel consumption and probability of road accident with serious injury. The analysis calculated the investment costs and the impacts on traffic, road safety and the environment expressed in monetary units and showed that the reduction of the speed limit to 80 km/h on the interurban road network in Greece is considered to be economically very positive for the society, with a positive economic Net Present Value (ENPV=€170.7 million) and a high ERR (ERR=39.1%).