Initially, choice of regular-interval timetable was mostly addressing operational concerns, aiming to increase the network throughput and to smooth the day-today tasks of the personnel. Separation between infrastructure management and train operations, induced by the European Union since the early 90s, and the future opening of the rail services to competition, pushes more and more infrastructure managers to operate their network with regular-interval timetable. 'Thus, the interest of measuring the degree of regularity.