Economic simulations tend to have less emphasis on the technical details of building railways and driving trains, but put you in the position of an entrepreneur trying to build railway lines and run trains to make profits from the passengers and goods carried. A few classic examples:

Railroad Tycoon

This is something of a classic. Quite believable in the 19th-century scenarios when you’re building lines to open up the North American outback, but a bit less so when it comes to the modern world, and especially to urban settings. 

Traffic Giant

Probably the most “technical” that I have come across — this is an urban transport simulation, where you have very detailed control over the schedules, routes and stops of your trams, buses, and metros. A nice feature is that the inhabitants of your city are simulated individually, and have very specific, predefined transport needs — if you don’t provide a bus route to their place of work, shopping area, or whatever, they will go by car and create traffic hold-ups. A disadvantage of this system, however, is that it doesn’t allow for urban development in response to your transport services. Providing a remote village with a fast service to the city doesn’t make anyone go to live there, it just leads to empty trains. Similarly, demolishing property to build new tracks reduces the number of passengers available.

Locomotion

This is written by Chris Sawyer, who was responsible for the original Transport Tycoon and Roller-Coaster Tycoon games. It’s fun in that you get to run all sorts of different transport modes: trucks, buses, trams, trains, planes, ships. Tracklaying is by snapping predefined shapes together, exactly as in Roller-Coaster Tycoon, which is less comfortable than some other games, but reasonably intuitive after a while.