This is a really simple mod which affects player's speed when walking on a vanilla grass-path.
When player walks on a grass-path (the one which made by right-clicking grass block with a shovel), his speed is increased (times 1.5x), you can even sprint on them to increase running speed as well!
Not sure if it's will be compatible with modded items that increases player speed, but it should (successfully tested and proofed to work with Sojourner's sash from Botania and Boots of the Traveler from Thaumcraft).
Since version 1.1 allows to alter entity speed on any block you'd like using config.
Please note: 0.1 is the base value of player normal speed, so keep that in mind when changing speeds.
Forge version 2772 or above is required.
Mod is a server-side only (not required on client, but doesn't hurt if it is in there).