I seem to remember that the track on the roof of the Fiat factory was used as part of the production process..? When cars came off the end of the line they were tested by driving them up onto the roof round the track and back down again which was thought to be a test of all systems prior to shipping..? I watched a UK TV prog in the 90`s (?)that showed production when the factory was in full swing. Could perhaps have been the UK TV documentary prog series Horizon, one of which I have posted before.
Supercharged Grand Prix Cars 1924-1939 (full version) - YouTube
Horizon (British TV series) - Wikipedia
