The Brazilian public transportation system is composed of small and medium size companies. These companies may not be prepared to thrive in a competitive environment because, generally, these firms are managed like a family business. Thus, Knowledge Management (KM) can be defined as an efficient and simple way to solve day-to-day problems and drive the quality of services. Knowledge Management System (KMS) is a business process developed to encompass a basic investigative process, which consists of a synthetic diagnosis of the general conditions and the establishment of programs aimed at the generation of improvements based on the reduction and or elimination of wastefulness. This paper presents KM methodology (KM and KMS) applied in three case studies in Brazilian bus companies. The results indicate that application of this methodology allows companies to reach a competitive advantage. This paper is a result of consulting services in these companies.