Grass, spike strip is a tad too extreme, could cause punctures....
Back when we raced there, it was 4 wheels off more than twice got you a naughty boy flag, then any more and you'd be out, we used to work on the theory that the observers never wrote stuff down so you could do it every third lap and get away with it, two wheels off were fine, but then there was a sodding great wall about 10 foot away to your left, nothing like a solid object to keep you aware of the track limits.
Don Truman was the worst though, I still have nightmares of him shouting "the green bit is mine, black bit yours, you're not fucking touring car drivers!" at the end of each drivers briefing.
