I see this is where my ignorance of rail operations is going to come shining through.  Please do forgive me.  A "line" that butts up to an industry or business that requires rail support is then called a spur?  I'll use two different examples to cover a wide range of potentials.  An industry such as a newspaper company that takes delivery of massive rolls of paper via a box car and a mining operation.  For the newspaper operation how then does the paper product get from the main line to the business?  Would the product be dropped at a rail yard then a short line operation move the product to the business?  A mining operation would fill ore cars for processing on a "spur". Once the consist had been completed how then would that consist make it's way to a processing plant.  Would the consist roll on the main with a dedicated loco or would the operator of the Class One line delegate how the ore got to its processing plant?  I guess the bigger question here is might there be a good book detailing rail operations at a basic level that I should read.  Suddenly the idea of putting together a layout seems slightly more complicated...if I wish for it to resemble something close to an actual rail operation.

So then main line track is typically Code 83, this I understand, and thank you all for this information.  It seems the more I learn the more questions are developed.  Take as an example a rail yard (that will be visible), if the main line passes through the yard this would remain Code 83?  Staging track in the yard itself would then be what, Code 70, Code 55, or would remain consistant with Code 83?    I would ask the same of rail that links individual business on the layout to the staging area, Code what (typically)?  I do understand that how the side rail is addressed or more accurately treated with regard to overgrowth, less ballast, a somewhat neglected appearance, to display a lack of heavy use will help convey that image however what code would be typical of that application?

Here then is presented an interesting situation.  I'm planning on constructing a layout modeling the mid 1950's.  Was Code 83 not standard during that era?  My initial thoughts were Code 83 for all track however it seems Code 70 might be more accurate given the time frame.  Then there is the convention of mixed track, Code 83 for main line use and Code 70 for branch line and or visible railyards.  As far as visually pleasing is concerned I plan on airbrushing the track, taking into consideration where the track is located and what its primary use is however from a connectivity stand point and smooth operation when mixing track from 70 to 83 to 100 (for unseen locations) I would suspect this provides a challenge?  I'm concerned that mixing 83 and 70 might provide for unreliable or unstable operations due to the height difference, would this be a valid concern?

Thank you both.  After finding some literature on line comparing 83 to 100 and that which your replies stared it sounds like Code 83 is the logical selection (true to the cause of accurate reproduction/modeling).  Thanks for the infomation, I really appreciate it.

Alan

I'm new to model trains.  That being said as I read about layouts I've not found anything that suggests which code track is better to use and why, if mentioned at all.  So my question to all of you experienced model railroaders is this: Obviously there is a height difference between 83 and 100 however what is the benefit if any of using one type over the other.  If the wheels of the truck are all standard with regard to the interior edge it should make no difference...right?  Any help would be greatly appreciated.  I plan on purchasing some flex track today however any suggestions would be graciously accepted.

Alan