Service quality has been regarded as an important issue since the 1980s. The measurement of service quality is harder than the quality of the product, since it varies from person to person and produces no concrete output. A number of models have been developed in the literature to assess service quality. The transportation sector is one of the leading components of the service sector. Increasing the quality of public transport has a strong influence in the development of cities and decreasing the usage of private cars. The quality of bus services is defined in accordance with TS-EN 13816 Standard, which allows measurement of the quality of public transport. In Istanbul, service quality criteria for buses are determined and their performance is measured systematically. In this study, factor analysis was applied to evaluate the quality of the bus services using the results of the Satisfaction Surveys applied by IETT to 2177 users on the internet and a multiple linear regression model was developed. When the two emerging factors are examined, it is seen that users pay more importance to access to the service than the comfort. In addition, the results of user surveys were compared with the views of service providers, and a difference of only 1.733% was observed between the two groups' views.