A few historical tidbits about railroad tracks:
When railroads started being built in the United States they used up massive amounts of lumber, partly because of the necessity for railroad ties, but mostly because these ties wore out extremely quickly - they needed to be replaced every five years. Something needed to be done; at that rate the entire North American continent would have been completely deforested by the beginning of the 20th century.
Coincidentally, around this time British engineers were trying desperately to get rid of coal tar, a byproduct left by burning coal for fuel. The stuff was piling up and nobody had the faintest idea of what to do with it. Some intrepid soul solved both problems at once by coating railroad ties in the stuff, increasing their usable life from five years to thirty by locking out moisture. Close shave, that.
Nowadays, though wooden ties are still predominantly in use, some interesting steps have been taken to further decrease the amount of lumber necessary. Some railroads (particularly subways because they run at much lower speeds than commuter trains) run with wood under each rail and none in the middle, decreasing the wood necessary by a third as well as allowing for water drainage down a canal located under and between the rails. Also, many higher speed commuter trains (like the Northeast Corridor AMTRAK lines which share their tracks with New Jersey Transit trains) are slowly replacing their ties as they wear out with a special kind of concrete that allows for the same standards of flexibility and rigidity as wood without killing off hundreds of trees to do so.
When I remember where I learned this stuff, I'll be sure to cite it.
The historical part came from James Burke's Connections series of books;
the source of the rest I've temporarily forgotten.