“SAM” stands for “Stand Along Map” while “SAM2” stands for “Stand Alone Map2”, there is no difference to the end users between the two. If  a file is marked as a “SAM” or “SAM2” that means it has been packaged in such a way that all you have to do is uncompress it and move it into your “My Games\Sid Meier’s Railroads!\UserMaps” folder.  This is a dramatic improvement over the method first used where one might have to download up to five maps and install them for a new map to work.   Now it may seem at first that this is really a regression, after all now you can only have one map installed at a time.  In this case though the benefits out weigh the cost quite a bit. Sadly some Sid Meier’s Railroads! files cannot be edited per map without chaning things for the entire game, an example of which is the tunnels.xml. The tunnels.xml stores the costs for both tunnels and bridges, many mappers like to change these costs to create more realistic maps.  As well the game has a fairly low limit of how many unique goods there can be in the game, beyond this limit the game simply ignores the other goods.  Perhaps though the biggest reasoning is that Sid Meier’s Railroads is not conservative when it comes to memory use and will load up every asset in the Sid Meier’s Railroads! folder it can find. By limiting the amount of unused files the game loads, maps can be made larger with the memory available.

The effort to get every Sid Meier’s Railroads custom map into the SAM format was spearheaded by Snoopy55, Bobby, Tijer and Pete colectivly known as STEP inc, credit also goes to Jancsika for pakaging a number of maps.

You might also incounter “Clean install Compatible” aka “CIC” pakaged maps, these can be installed jsut like  “SAM”s would be by copying the files into the “My Games\Sid Meier’s Railroads!\UserMaps” folder.