On-board bus comfort is a key factor affecting the quality of transit service. Thus, its assessment is crucial for public transport companies, as it can support the monitoring, evaluation and implementation of specific actions to improve their services. Previous research mainly focused on separate subjective and objective measurements of on-board comfort. Furthermore, even if concurrent measurements of objective and subjective on-board comfort have been collected, no study has built a gradual scale for the real-time measurement of comfort. This paper covers this gap by integrating subjective measurements of driving style with objective measurements of longitudinal and transversal accelerations collected by intelligent transportation system tools. These findings are very useful because they represent the first contribution for establishing a comfort scale in a real operational environment as a tool to regulate driver behavior, i.e., each driver will be able to recognize when passengers experience conditions of discomfort and acts to improve comfort.