This proposal is complementary to the proposed southern tangent line in Budapest. It is an urban-regional metro line, comparable to ‘S-Bahn’ (German-language) or ‘RER’ (Francophone) lines. It would use the same alignment and stations, between Kelenföld Station and the junction with the line Kőbánya-Kispest Station. It also shares an alignment and stations with the proposed eastern tangent line from Nyugati Station to Kőbánya-Kispest. It would connect with some radial lines of the proposed Budapest urban-regional metro. It would not provide a connection from Kelenföld Station to Kőbánya-Kispest Station, but that is unnecessary since the southern tangent line would go there directly.
The ring line would follow existing tracks, with one exception: a new link between Horog utca and Pongrac út. On this section, there would be a new station, opposite the main gate of the exhibition centre Hungexpo. On parts of the route, additional tracks would be necessary, and all junctions should be grade-separated.
The ring line would start, like the south tangent, at Kelenföld Station. It would cross the Danube, with a station on the west side of the bridge (ELTE), and possibly on the east side (HÉV interchange). It would pass through the existing Ferencváros Station. There would be a new interchange station for metro line 3, at Ecseri út. At the next junction, the south tangent line turns south-east to Kőbánya-Kispest Station: the ring line continues north-east, and crosses Kőbányai út. A station here would be problematic, because it is between two rail junctions.
Just north of Kőbányai út, the new section diverges from the existing line. A tunnel seems the only option for this section: it would pass under the Csilla utca and the Salgótarjáni utca, and join the existing ring line, west of the Hungexpo centre. The new station here, would be about 200 m from the main entrance to Hungexpo. This alignment means that there is no connection with line to Rákos station (on line 80 and line 120).
From the junction, the line shares the route of the proposed eastern tangent line. Both lines cross Kerepesi út, route of Metro line 2, with a new station for interchange with metro line 2: Pillangó utca station is about 400 meter to the east.
A new station is also possible at Egressy út, although the station spacing is a problem. Along with the eastern tangent line, the ring line will also serve the existing station at Budapest-Zugló, future interchange with the new metro line 4. Both lines would serve a new station, alongside the Mexikói út metro station (metro line 1).
Click to enlarge: the proposed east tangent S-Bahn line..
The eastern tangent line would now turn south-west, toward Nyugati station. The ring line would follow the existing curve north to a relocated Rákosrendező station, on the main line north from Nyugati to Vác (line 70 / 71). The ring line could terminate there, or possibly continue along line 2 across the Danube, to terminate at Acquincum station, relocated for interchange with the HÉV line to Szentendre. (The rest of line 2 to Esztergom might be incorporated in the planned “metro line 5”, which incorporates the three HÉV lines along the Danube).