I've done a quick example to show how effective bump maps are. Keep in mind this is an example that took me a minute to generate. For a game I'd spend several hours perfecting it, I'd also do the rails as seperate piece of geometery. You start with some geometry, in this case a flat plane, just one polygon. You then add a texture. Then finally you add a bump map. The bump map tells the game how the light should be cast across the surface, so although it looks 3D it's not, it's just an illusion. Whilst it's not as good as using the actual geometry it's a lot less costly to render in game but still looks pretty good.