TRAINS CHASING THEIR OWN TAILS
While some of our layouts with longer trains may seem strange to the point they are chasing their tails,  in Carmangay Alberta, Canada there is a huge loop to the grain silo where a train can come in form either direction, run around the loop and drive out loaded up in the same direction.  

The aerial view is

Google Maps and the oblong oval is easy enough to pick  out… complete with trains.

I was sent a picture today from a friend in the area where the lead engines were within sight of the last loco as a distributed power unit or DPU.

TROLLEY POLES ON DIESELS?
Pacific Electric in California had a number of freight locomotives. When they were replaced by diesels but the traction lines kept running, the diesels were fitted with trolley poles so that Pacific Electrics signalling system would work. 

You might think some of the "half pipe" type tunnels sold with train sets are not prototypical and for the most part, they are not.  
However, due to seismic shifts inside a tunnel on Canadian Pacific, the tunnel was daylighted in the 1970's except for the concrete lining which was left in situ to protect trains against landslides and avalanches from the slopes on either side. I believe that it was fully daylighted in the 1980s but a common sight on model railways was replicated for a reasonable length of time.

WHEN TRAINS TRAVEL IN ONE DIRECTION ONLY
There are a number of tracks in the US in particular where the trains only run in one direction.  When the Burlington Northern was formed in part from Great Northern and Northern Pacific, two lines became one directional because the gradients were easier.  The UP west of Cheyenne also has a couple of single direction lines.   The Southern Pacific and Western Pacific had two parallel lines across Northern Nevada which they jointly ran as though both had double track although the railroads were up to 5 miles apart in places.