Whenever there's a realignment to a road or a new road project there will be one or more sections, however long or short, that aren't needed as much anymore, if they're still needed at all.
So what becomes of these bypassed roads?
In urban areas, a new freeway will ease the congestion on the corresponding section of highway.
In regional areas, this can mean far less traffic coming through town (which is not so good for business it has to be said).
You can see this for yourself if you look more closely. In a substantial number of regional centers, what used to be part of the highway is now just the town's main street.
It always was the main street, of course, it's just that the bypass wasn't always there. And now the old section is used to get into, through, and out of town for those who do need or want to stay or visit.
In some cases the bypassed road is of interest to visitors exploring the region.
Plenty of tourist drive routes traverse these old roads, encouraging travellers to still go through the region's townships (in the hope they stop for a better look and maybe spend a little money while they're there).
In quite a number of cases outside of townships, the bypassed sections become local or access roads, used to get to properties and that's about it.
Some rest areas will get created on the old section of highway, which may then also be used as on and off ramps to access them.
If they can serve no other purpose, some of these disused sections get removed partly or completely, with grass growing in their place.
Some sections may not be cleanly or completely removed however, and now find themselves to be on a private property (after an adjustment of property borders to suit the new road alignment).
Then there are those sections that get repurposed into something that has nothing to do with traffic of any kind.
One example that comes to mind is the Mt Cooperabung hillclimb track in NSW, found roughly halfway between Port Macquarie and Kempsey and operated by the Kempsey Sporting Car Club.
This, treacherous if we're honest, strip of black stuff with a couple of tight climbing bends between the trees is a former section of the very old Pacific Highway.
It can only be accessed at one end (and that changed with a second realignment), the new alignment carving into the hillside making it impractical to have the additional connection at the far end.
The club has had to put a decent amount of effort in to maintain the surface too, and it presents a serious-but-rewarding challenge in the wet because the grip levels change so much between the old and new top layers.
Organisers have other challenges too. A lack of funding from outside sources does mean a lack of facilities. Every outbuilding, let's call them, has to be hired. It's also completely surrounded by bush, so fire is a concern but it's actually severe storm warnings that have seen events called off in the past.
They are a CAMS-sanctioned club with a track licence, and in addition to the local and interclub events they are a round on the NSW Hillclimb Championship calendar each year.
So, maybe this has got you thinking about a disused bit of road near you that could be legally repurposed for something useful.
Sam Hollier is an ACM journalist and a motoring fanatic who builds cars in his shed in his spare time.