A friend is building a combination HO and HOn30 model railroad and he's decided to hand-lay the track. He has cut the wooden ties and was getting ready to color them when he noticed something was missing. It was the railroady smell you get when walking the tracks.
The smell is from creosote, the tie preservative. New wood ties are soaked in creosote under pressure to preserve them.
Over 50 years ago Tru-Scale offered real creosote tie preservative for model railroaders. I still have a can and remember using a little of it on a railroad I once built.
Needless to say I gave the can to my friend so he can have a model railroad that smells like a real railroad.