This paper investigates the efficiency evaluation of a public transport using an analysis of Origin-Destinationmatrices (mOD). The use of a trip-chaining method on the automatically collected transport data providesa realistic and accurate representation of traffic flows characterized by mOD. The introduction of a criticalwalking distance and an user flow at bus stop allow us to probe possible network configurations and identifythe best one in terms of service offer, ecological impact and operational cost. The configurations comparisonallows to identify the levers for the transport management. We deploy this methodology on a french case studyfor the Toulouse Metropole Occitanie region. The main obtained results shows that for a walking distanceclose 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 thatlow-cost optimization of a transport network is possible while maintaining a high-quality, environmentallyfriendlyservice offering.