Yeah tyres, if anyone can every find a efficient way of recycling tyres into another product you would make millions. Was doing research on it in university. I want to find a way to make window frames from it, then I can be a millionaire and have the best micra lol
But yeah, race tracks like to put them in the way of things moving fast, Cadwell Park filled theirs with concrete last time I was there!
Or just be quick at the dump and hope nobody sees you.