Extends faster underground belts to lengths relative to their speeds (in vanilla, this means fast underground belts go twice as far as normal underground belts, and express belts three times as far). Also adds the appropriate number of "surface" belts to the recipe. Specifically:

Underground belts (underground distance 5, one pair spans 6 tiles) now cost 6 transport belts instead of 5.
Fast underground belts now span 12 tiles and have had 6 fast transport belts added to their recipe.
Express underground belts now span 18 tiles and include 6 express belts in their recipe.