I just found a page on the Atlas site with a little info on code 80 and 55 track. Go HERE --->
http://www.atlasrr.com/layoutfaq.htmand scroll down to N
OR, let me try to paste the info HERE:
N TRACK Frequently Asked Questions
Why should I use Atlas N scale track on my layout?
Atlas has been making N scale model railroad track for over 25 years. We are known throughout the world as one of the most prominent track makers in the hobby industry because of our high quality products and incredible performance. Our track and switches are made from injection-molded plastic and nickel silver rail so that you can be sure the layout you will build will be dependable. What's more, Atlas track is surprisingly affordable.
I've decided that I'm going to model in N scale but I'm not sure whether I want to use Atlas' traditional N scale Code 80 track, or the N scale Code 55 track. Can you please describe the differences between these track lines?
N Scale Code 80
Atlas' popular line of N scale Code 80 track is well known for its high quality and durability. With black ties and nickel silver rail, Atlas' N Scale Code 80 Track is sturdy, reliable, and looks great on any layout. The Code 80 line is very extensive and includes the popular Snap-Track®, Snap-Switches, Super-Flex® Track and more.
N Scale Code 55
Atlas' N scale Code 55 track was designed with the scale modeler in mind. Featuring simulated brown ties and a lower rail profile than N scale Code 80 track, Atlas' N scale Code 55 track is quickly becoming a favorite of N scale modelers everywhere. As with all Atlas track products, you can expect durability, flexibility and reliability with the N scale Code 55 track.
I've heard that some rolling stock may not run on Code 55 track. Is this true?
Some older rolling stock may have problems on N scale Code 55 track because of the wheels that do not comply with NMRA standards. You can run your favorite cars on our N scale Code 55 track by simply fitting your existing cars with a low-profile wheel set (Item # 22134) available from Atlas or several other manufacturers.
Where do I start?
The next step is to review the various layouts in our N scale Layout Gallery. Simply choose one and you're ready to go! Or you can download our popular layout planning software FREE! Click here for more details.
Atlas N Scale Track Summary
N Code 80 (Black Ties/Nickel Silver Rail) - Basic Line
N Code 55 (Brown Ties/Nickel Silver Rail) - Modeler's Track