The city of Zagreb and its surroundings form the so-called "Zagreb ring" in which the most intensive railway passenger traffic in the whole of Croatia takes place. This part of the railway network also includes the section of the Zagreb Glavni kolodvor - Dugo Selo railway, which according to the number of trains and transported passengers is one of the most significant sections in relation to the complete railway traffic of the Republic of Croatia. On that part of the railway, one of the problems is the section Sesvete - Dugo Selo because the Sesvete station is considered a bottleneck during daily peak loads. One of the solutions to this problem is the introduction of the European Level 2 Train Control System (ETCS - 2), which means the complete equipping of trains running on the observed section and infrastructure. This system facilitates the organization and development of railway traffic, improves the capacity of the railway and reduces the time of occupation of the tracks in the receiving - dispatching stations. This train control system makes the timetable much more stable and provides more space to correct and regulate trains in case of emergencies. Another solution to increase the capacity of the given line is the development of a new clock schedule with a recommended time interval between two consecutive trains of twelve minutes, the focus is on suburban trains which have the most in peak loads. The mentioned measures and proposals were tested in the computer package OpenTrack, where in real time the railway traffic can be simulated with the existing system and timetable and compared with the proposed changes.