The aim of this paper is to study empirically the energy efficiency of the production of public road transport services in the region Sfax-Tunisia: case of the regional transport company of Sfax (SORETRAS). To do this, we proceeded to synthesize the main works that dealt with this subject and we collected a database from the company during a period of study from 1986 to 2017. Indeed, the theory of Co-integration and error correction model were used to analyze the linear fit quality of the impact of energy on the energy efficiency of the SORETRAS.