Weeds are significant issues across Australia and I often think about what the country would look like with intact vegetation and no lantana or the many other weeds that are invading natural bushlands and in some cases smothering them.
There are numerous pieces of legislation which outline declared pests. Here in Queensland, we have the Land Protection (Pest and Stock Route Management) Act. Local councils also quite regularly identify lists of environmental weeds, these are usually invasive species that are non-native but widespread and unlikely to be completely removed from Australia without significant effort and investment.
Weed control in your own patch of land is important, but where opportunities present themselves it is important to undertake weed seed spread prevention methods where available. I came across a public wash down facility when I was in North Queensland a couple of years back.
I thought this was a great initiative but I don't think many other drivers on the road where even aware of the facility (it wasn't mandatory and you almost had to know it was there to see it) and certainly didn't seem to be using it. Therefore it probably wasn't very effective at this location, but you never know.
Here is a photo of the wash down facility in action.