HI everybody! I would like to add a passenger train to my layout. The problem i see is that passenger cars are - hu - so very long. I am using 18 degree curves, i have got several mountains, one of coarse with a tunnel. The track enters the tunnel on a curve, (1 mistake) i can invision the long passenger car entering the tunnel and coming in contact with the side of the tunnel portal! Maybe my passenger train will have to be reserved for a future layout. Any comments or suggestions will be welcome. Happy railroading!! 
Though they are not the best quality or most realistic looking, IHC and Athearn passenger cars run fine on 18" curves.
Athearn’s streamlined and heavyweight “generic” passenger cars are a scale 72ft. long and will easily negotiate 18" radius curves. Below is an
http://www.athearn.com/Products/Default.aspx?ProdID=ATH7904
http://www.athearn.com/Products/Default.aspx?ProdID=ATH7964
http://www.athearn.com/Products/Default.aspx?ProdID=ATH78772
Is there a particular railroad and time period that you’re interested in?
Your best bet with sharp curves might be to go with a passenger train from an early era, like pre-1900. Prototype cars and locos in that period were short and were designed for the sharper curves of the era, which scale down well for your models.
An alternative for your tunnel problem: substitute a double track portal to give you more clearance. The scenery on the approach can be made to look like there were originally two tracks going into the tunnel, but modernization has reduced that to one track and centered it for better clearance of the larger, newer cars.
I’ll ditto the Athearn cars. Roundhouse/MDC also makes 34’ Overton passenger cars - these are from a pre-1900 shortline for prototype, but look neat running behind a 4-4-0. My [2c]
You do not say what railroad you are modeling. CNW had some shorter cars that Walthers made as kits many years ago that may be available on E Bay. At the PRR convention a couple of weeks ago a major manufacturer had some test shots of PRR P-54 passnger cars that were the basis for the MP54 commuter trains. They are 54’ long and really looked good. I would expect them to be available in the near future.
Hi!
For “regular” passenger cars, the Athearn’s can’t be beat. I built up a set of heavyweights with diaphrams (spell?), KDs, window tint and Intermountain wheelsets. They really look and run nicely, especially behind a steam loco. I also have a set of the Athearn lightweights (with add ons) and they don’t look too bad - especially behind an F unit consist.
All that being said, 18 inch radius track is really too small to show off a passenger train - with the exception of the old syle Overton type cars. It sounds like you are using sectional track, and I would urge you to look to moving up to 22 inch radius track for a much better setting.
Hey, for what its worth…
Mobilman44
I would suggest you look at the Roundhouse Overland coaches or the Hornby Rivarossi 60` coaches for your smaller radius layout.