The different Audiosurf roads occurs because of different .ash files. The .ash files are files generated by Audiosurf that show the shape of the track, the distribution of blocks by color, and traffic rating. As soon as you load a song for the first time the game generates the .ash file. It is possible to have different .ash files for the same song because of the different formats (.mp3, .m4a, .ogg, .wma). I have had 3 different .ash files for the same song: one from a CD, one from iTunes, and one .mp3 download. There are also different versions of a song such as an original version or a live concert version that are posted on the same scoreboard.