...hmm...you should be able to either just fine. The only trouble is...the trains in RailRoads! will always take the shortest route to their next destination. This means that the "loop" makes the train travel farther...it would be easier for it to just flip around and travel straight back (which just looks dumb, I agree)...but I made the loop and "Y" just fine.
The bottom picture is from a map I am building...I use a large Y for my wood - paper - deliver to the next town - then return track. The train will follow the Y because it is the only way for it to get back to the lumber yard after it drops off wood, picks up paper, drops off paper to the next town, then needs to return to repete the cycle.
You have to watch the light towers...
connect the track in the middle of the towers...when the lay track arrows are green...then the tower will have two lights at the top. Like Snoopy says...lay your track up to the tower and stop...then start from the center of the tower and work back to where you stopped connecting the track. You
can do loops on bridges...but it takes a bit of work and you have to raise the track up for them to connect. The game likes to CTD when messing around with bridges so it may take a couple trys and saves as you go. Simply save it in sections...then if it drops to the desktop just go right back in there and finish it.
EDIT//
Oh...and your comment about the extra end track bumper...
sometimes in railroads...(often
)...it will stick an extra small section of track off of a light tower or at an intersection with a station platform. All you need do is keep clicking till you highlight the small bumper and delete it, the tower will drop off one light and you will then be able to connect your track. Remember to start from the towers middle -or- main track line and work outward.