This paper investigates the efficiency evaluation of a public transport using an analysis of Origin-Destination matrices (mOD). The use of a trip-chaining method on the automatically collected transport data provides a realistic and accurate representation of traffic flows characterized by mOD. The introduction of a critical walking distance and an user flow at bus stop allow us to probe possible network configurations and identify the best one in terms of service offer, ecological impact and operational cost. The configurations comparison allows to identify the levers for the transport management. We deploy this methodology on a french case study for the Toulouse Metropole Occitanie region. The main obtained results shows that for a walking distance close to 1000m, the distance per day on a bus line can be optimized by 3km for a time saving close to 20%, representing an annual gain of more than 1ton of CO2 for a user loss of around 3%. These results suggest that low-cost optimization of a transport network is possible while maintaining a high-quality, environmentallyfriendly service offering.