I've had this idea about a very special mod for several months now. It's so very unusual that it only takes a minecart ONE whole block to turn 90°. Wow, how...inovative? Wrong! The idea is to have a mod that requires you to plan out how wide a turn must be for a minecart to turn, requiring a rail piece to have certain sizes like 2*2, 4*6, and so on. In addition, the mod could be made to work with rail based mods like RailCraft.
Mo' Railz!