505 and its train formed of I type trailers 1719 and 1720 head outbound through Karlsplatz.

The I type trailers were originally built as I3 trailers but in this form could not run in pairs as shown here. Many were rebuilt from 1973-76 and re-designated to distinguish them from unrebuilt vehicles. The trailers given designations beginning with I were the only ones designated with a capital letter, normal practice was that motor cars had a capital letter and trailers a lower case letter.

Photograph by courtesy of Phil Sposito