Anyway, the problem is at the bottom, when it meets the main coastal highway in a roundabout. And if you have a busy day on the highway - like Boxing Day - then you can get about one car a minute off the Canberra road and onto the main coastal road. And when they're arriving from Canberra at the rate of one car every ten seconds ... by mid-afternoon there's a massive queue that can go for miles and take over an hour to get through.
So I thought I would investigate something marked on Google maps (and our road atlas) and take the Runnyford Road. It was a bit of an adventure - it took 40 minutes to go 22 km. All unsealed (very slippery gravel) and narrow with quite steep embankments through the state forest and no safety rails or anything. This photo is pretty much the only bit I felt safe to pull over and take a picture. It was very pretty. In the photo below you can see the road through the trees - typically winding down to a stream, then a concrete ford, and back up again. It would have been better in a 4WD and not my tiny little Polo :).
So I don't think it's going to work as traffic avoidance, especially not if we were in a hurry or had fractious children or it was 40 degrees ... or if there had been rain in the last five days which I think would make it impassable! I didn't see another car the whole road, and maybe two houses, so perhaps not great if you did have an accident.