Normally in your budget you have to pay 100% for transport in order to prevent the roads/rails from deteriorating. If you drop it to 0%, then most the railroad tracks and roads will go away. However, the bits of railroad that have electric power lines going over them will stay! In order to exploit this glitch, build as much railroad as you want, being sure to put a piece of electrical wiring over it. Then set your transport-maintenance cost to 0% and watch as you pay nothing and your railroads do not deteriorate!