I have two older passenger HO sets. 1 are the pullmans which are illuminated and the others are the alasken passengers. I forget the radius they need because of the length of the cars. I am going to run both side by side on an elevated monorail platform support type. Each will run above the main layout. the curved section will be on a mountain side at each end of the room and then both straight sections will be on girdle bridges I am building. length from end to end is 14 foot. Does anyone have any idea on the track radius for the curves pertaining to the passenger cars?????