The population of Northwestern Croatia is traditionally focused on the railway and gravitates daily to the wider Zagreb area. The most intensive passenger traffic on the Zaprešić – Varaždin line is realized on the Zaprešić – Zabok section, and passengers from Đurmanec and Gornja Stubica are also gravitating to Zabok. For this reason it is planned to include mentioned section line in the suburban transportation system of the city of Zagreb. In order to achieve this, its modernization and electrification is needed due to the poor condition, so in this graduate thesis the current and future state of the infrastructure in this area is being considered. For the analysis of the existing and future passenger train organization and train traffic, a computer program for modeling in the railways OpenTrack is used. On the future suburban passenger transport line Zagreb Main Station – Zabok there are proposed four new variants of passenger train organizations that are compared with different parameters to better define the most suitable variant for this line.