Source: German Federal Archive:
http://www.bundesarchiv.de/gedenkbuch/directory.html?id=1006394

At least in the case of the December 11, 1941 transport from Düsseldorf, the train was composed of third class passenger cars for the Jews and a second class passenger car for the guards. Apparently efforts were made to keep the train heated. Source: http://en.wikipedia.org/wiki/Riga_Ghetto#Jews_from_Germany

German Federal Archive: http://www.bundesarchiv.de/gedenkbuch/directory.html?id=1006948 erroneously mentions Dortmund as the place of transport for Margarethe Kaufmann, geb. Kahn.
In the Riga Memory Book under the name-lists of killed people, Margarethe Kaufmann, geb. Kahn is listed as being on the Duesseldorf Transport.
This seems to be more acceptable, as her last registered address was with her daughter and grandson so they were deported together.

Gunter Demnig laid the Stolperstones in a ceremony that was witnessed by about 50 people: the mayor of Nettetal-Breyell, members of the town council, the church organizations who together with the Lienen family (Vera, the initiator of this project and her brother) sponsored the stones.