Max9 we have similar technology on our freeways (limited speed though). The problem is when you get out into the country, the distances are just too vast to fence. And kangaroos can jump! We would need BIG fences to be roo-proof.
To put things in perspective... if you and I left home at the same time and drove at 110km/h for 24 hours, I would still be on the same road in the same state. You would reach Istanbul!