This is a paid asset, but now you can download Road Texture Pack Game-Ready Free.
Detail this asset from Unity Store: Original Link
Road Texture Pack Game-Ready v1
“If possible, please buy the package to support the developer”
A selection of 7 high Quality, 1024 x 1024 fully tile-able game-ready road terrain textures.
Unity 5 Ready! Assets come packaged with Game-Ready materials and Source Assets including Normal Maps, AO Maps. Albedo and Height Maps.
Unity 5 Game Ready Materials Included!
A Full suite of Game-Ready Road Tarmac Materials, including source Albedo, Normal, AO and Height Maps. Source Material coems in both PNG and TGA format!