This master’s thesis describes the design of the Domžale – Brnik – Kranj railway line with connection to the existing railway line Ljubljana – Kamnik Graben and Ljubljana – Jesenice d.m. In the first part of the thesis, we present the main points and short development of the TEN – T network in the EU and in Slovenia. Further, we describe introduction of the railway to the suburban areas, and importance of sustainable mobility. In the second part of the thesis, we describe the boundary conditions of the route, which influenced the choice of variants and tools and substrates used in the design of the railway line Domžale – Brnik – Kranj. In addition, this section also describes the technical requirements that determine the starting points for the design of the railway line. Three different variants of the railway lines and their placement in the space are presented. Further in the second part, evaluation and evaluation methodology of the three variants and selection of the most suitable variant are presented, which are then optimized. In the third part of the thesis, technical data are given on the selected variant with all the technical elements of the railway route, the calculations of linear speeds using the program for calculating travel times between stations and the timetable, with which we evaluated the frequency of trains, which would be allowed by the monorail connection Ljubljana – Domžale – Brnik – Kranj.