Berger_fan, yes you can use the same texture for track as for run off etc. however they will not look the same in game, gp4 adds som other textures, jams i think, and skids ets which overall makes the tarmac look darker, however for monarco i was intending to try and match a few bits up.
texture sources, grass and trees and some fences from race driver2, others from f12001, serial mikes high res updates(with permission of course) and a few ive had to make from scratch. race driver 2 had some of the best textures which can easily be altered in photoshop toi get what you want.