I spotted the zigzag line across the road on the way home from Geo Toroa Mega and thought this road needed some fresh caches.
I was slightly puzzled - not only by the way the line zigzags, but the sign here is a GORE sign, not one for Southland. Then realised that the one on the other side of the side road is for Clutha, not Otago. Hmm.... Aha!
The line across the road on the map shows the bounary between Otago Region and Southland Region. Each region is divided into several Territorial Authorities - known to us as District Councils and City Councils. Or so I thought. But this is not always the case. As I found in that link Territorial authority districts are not always subdivisions of regions, and some territorial authorities fall within more than one region (see this map).
According to wikipedia, regional council areas are based on water catchment areas, whereas territorial authorities are based on community of interest and road access. Regional councils are responsible for the administration of many environmental and public transport matters, while the territorial authorities administer local roading and reserves, water supply and sanitation, building consents, the land use and subdivision aspects of resource management, and other local matters including animal control. There are some parts of New Zealand where Regional and Local councils have combined to form a unitary authority. It has recently been suggested that this could happend with Environment Southland, Southland District Council, Gore City Council and Invercargill City Council.
Local roads to each side of this highway are maintained by the local council, but as the road itself is a highway (it has a number) so is not the responsibiity of the local councils. Things are never clear cut!
Whichever way you are heading, enjoy your journey. Parking is on the "into Southland" side of the road, so if leaving I suggest you turn up into the side road.