I think that part of the video is mislabelled. What you're seeing is the Glenelg Tramway going over South Road, and the Emerson Overpass appears in the background just before that scene fades out.Cruise Control wrote:Also, that showed a 3 lane underpass at anzac highway and the same at cross roads why would you demolish a perfectly good overpass?.
And now the controversial bit: I don't think the plan's that good!
For a start, the cost estimate is wildly optimistic. Extrapolating from early estimates of the cost of a much shorter tunnel doesn't seem to be a good way of estimating the cost of a tunnel a few km long, especially one that goes under the River Torrens! And the land acquisition for the widening of South Road to 3 lanes each way would also be very expensive.
This plan would not even make South Road free flowing. For that you'd have to provide grade separated crossing points for pedestrians and block off or grade separate all right turns and other roads that cross South Road. The ones where overpasses and underpasses are proposed are not enough - consider Edward Street (Melrose Park) that is part of a bus route. As, for that matter, is Flinders Drive! And the video shows they're not even planning to grade separate the Southern Expressway - South Road junction at Bedford Park!
I know from what I've seen in London that roads like South Road CAN be entirely grade separated, and even partial grade separation can bring significant benefits. But is doing so cost effective on South Road? Apart from the major bottlenecks that the state government has already committed to fix, I think not.
Improving our rail infrastructure so that it provides a viable alternative for more people should take priority, as this would reduce the number of vehicles on the road, and would not reach capacity so quickly, and its journey times wouldn't be significantly affected by the number of people using it.
Eventually, when SA's rich from all the mining activity, and the Southern Expressway is two way throughout (plus a railway alongside Stage 1) it would be a good idea to build a North-South tollway, but that would probably be better suited to a new alignment (mostly underground, but with some elevated sections in non-residential areas). But trying to turn South Road into a freeway is not such a practical solution. Even if it were widened, it would still become gridlocked in the peaks.