[flamingGalah!]

Originally Posted by Chewy

I like how they have an actual freight train on the viaduct too lol

That's because where the original exterior set was built, on the other side of the Bonded Warehouse building, it had a real railway line going past the back of it... Which was a stroke of luck as the first street set (indoors) had a viaduct at the end of the street...

This area later became New York street on the Granada studios tour...