Trains set on easy will run through each other during conflicts. Set on Medium, they will pass through each other after a wait period. Set to run on Hard routing at the start of the game...will make trains use "open-blocks" or pathways to their destinations. I run my maps on Hard routing making a passenger rail and then a cargo rail with sidings for each...making each rail a duel rail. This helps.
One method is to take a certian train engine and make it pull say class 4 car types or whatever you name it...it could just as well be called a <szCar>_bnsf</szCar> for that matter. Then name your cars type in the TrainCars.xml listing as well...in this case the Gold car. This way no other train can pull the Gold car unless they have the same type number.
As to making them "stick" to a certian rail route that may be tricky. They will take the shortest route...but the block would have to be open.
Haven't been here in ages...I post my work at anouther site, and will be adding all my game mods to my web page soon. I build my maps in what I call a CIC style structure. Clean Install Compadable. Everything is inside one file folder and an Assets folder inside that along with all files needed to run the game. New trains everything. My files "replace" what the game loads when starting. This allows me to build gigantic maps with new stuff...and the game Only loads my stuff. In this manner the game won't load everything on the planet and the kitchen sink and use more resources. Hench the game runs super smooth with maps size 18 and larger...given your system has enough memory.
To run my maps...you have to empty out the files inside the Custom Maps folder...just store them elsewhere for now...Plus take and move everything out of the User Maps folder as well. It is very important you have all xml lists and other game files removed from those two folders...MyGames/SidMeiersRailRoads/ User Maps and Custom Assets folders.
Then...place the unzipped map folder inside the UserMaps folder. Start the game...scroll back one map and there is the new mod map...enter game.
Two maps are available at this time, there are others...they will be released later this month and a couple more after that.
I thought you might want to look at the file structure I use and just what I did and how I get things to work so well. Feel free to dig-in and maybe you may see some things you may want to do. On Mud Skippers you will see Industries that give only a small amount of a certian item...but if you send it other stuff...the production increases. The same for Holidays In Ohio...these are old maps...Florida Gold is being revamped for new engines and more and is about 90% complete.