Al,I bet your track has all the plastic frogs on the inside,and that's the side that gets dirty.I ran Atlas C80 on my last RR.On the bottom two tracks,there were no switches.The double track railroad just ran around and through the landscape,a way I could run large trains on a small RR,the actual "railroad" started on the second level.The bottom two tracks kept relatively clean,the top was horrible.Only difference was the plastic frogs,and they were on both sides of the track....