ExCon90 wrote:In Munich in the 1970's a double-track S-Bahn tunnel was constructed beneath the city center, with five intermediate stations, each having two side platforms and one wide center platform.
Only two stations apply this principle:
- Munich Central Station
- Munich Karlsplatz / Stachus
At a third station, Munich Marienplatz, the two tracks are arranged in parallel tunnels on top of each other; each of the tunnels has platforms on both sides at this station.
These three stations all also serve as transfer stations to the subway network located in further sub-levels, although at Munich Central Station only indirectly (gotta get one floor up, walk through the entire station at level -1, then go back down two to three levels).
The remaining two stations of the tunnel
- Munich Isartor
- Munich Rosenheimer Platz
were built conventionally with a center platform only.
As for "essential" that's very relative. Plenty of tunnel stations with higher train frequency and no Spanish Solution in Europe...
For the new second S-Bahn tunnel under construction, located at level -5 or -6 and about 40m underground, the two stations in the city (Central Station and Marienhof) will both get Spanish Solution platforms. Additional cost for these platforms at the two stations was about 100 million USD in planning - since then costs for the overall project have risen from 1.2 to 4.5 billion USD though.