The Grorud and Furuset Line head northeast into Groruddalen, while the other two eastern branches head south into Nordstrand. On the west side, the Holmenkoll and Sognsvann Line cover the northern boroughs of Oslo, along with the Ring Line that connects the northeastern and northwestern parts of town. The Kolsås and Røa Line reach deep into the neighbouring municipality of Bærum.  All the lines run through the Common Tunnel before reaching out to different lines, or into the Ring. All lines have a base service of four trains per hour while line 2 and the eastern section of line 3 have eight trains per hour weekdays 7–19. The eastern section of line 2 also has eight trains per hour Saturdays 10–19. A reduced half-hourly service operates on all lines during early weekend mornings. Trains run from about 05:00 (06:00 at weekends) to 01:00 the next morning.