The motorway A100, sliced into the city in the 60ties and 70ties, follows the circular rail.
When coming to Berlin in 2000 i wondered about these abandoned platforms at the stations of the circular rail, like the one you see on the right, at Station "Messe Nord (Witzleben)". And i spotted unused busstop-structures at the motorway. I had to use the wikipedia, to learn this:
The circular rail was run by the GDR-Reichsbahn, even in West-Berlin, so a lot of West-Berliners boycotted it.
1980, after a strike of the GDR-stuff, the circular rail was shut over night. It is reopened now, but some lines run different, so some platforms seem to have remained it the state, they have been left 1980.
As an Alternative, there were bus-lines on the circular motorway A100. The busstops were directly at the motorway, and there were stair-structures, to acess them. The first i spotted was one at Jakob-Kaiserplatz, i sketched last year and that is now demolished.
At Messe Nord (on the todays drawing on top) the stairs, that lead to the motorway-busstop below are harder to find: The entrance seems to be in the cubic building at the very left, that now contains the "bistro guenes" (in summer 2009 right) - i have visited and sketched this several times, without noticing its hidden history.