[COM] South Road Superway | $842m | 3km

[Paulns]

If you can't drive a truck without straying into another lane you shouldn't be on the road.

You missed the point.

[drsmith]

I think it's safe to say that it isn't. Once it gets past Days Road there's no need for direct right turn access, so extending the viaduct further S would just be a waste of money.

As for tunnelling, it would probably be cheaper to do it on the existing road alignment. But it would be difficult to justify the costs of tunnelling this far N. An underpass beneath Regency Road is more likely.

According to Superway Project Impact report (Alternative Designs Considered) the alignment of the north-south corridor south of Regency Road is still yet to be decided so it does appear that the southern end of the superway has indeed not been planned with a specific connection option in mind further south.

With an underpass at Regency Road surely some solution would have to be found to seperate local traffic from through traffic south of Regency road otherwise the local traffic there would find it very difficult to enter the roadway against a constant flow of traffic from the north. What alternatives are there in the absence of a new corridor for through traffic south of Regency Road (viaduct, tunnel or otherwise new alignment) ?

Interestingly too, one of the reasons underpasses were not chosen along the superway route was because of the water table. Could this potentially be a problem with underpass/tunnel options further south (Regency Road, Torrens Road, Port Road, grange road) ?

http://www.southroad.sa.gov.au/__data/a ... idered.pdf

[Wayno]

Interestingly too, one of the reasons underpasses were not chosen along the superway route was because of the water table. Could this potentially be a problem with underpass/tunnel options further south (Regency Road, Torrens Road, Port Road, grange road) ?

i was thinking about this just yesterday

With the Anzac/South Rd underpass, where does the rain water go? presumably the depth of the underpass is greater than the depth of storm water piping? is pumping used as a solution?

[Xaragmata]

Interestingly too, one of the reasons underpasses were not chosen along the superway route was because of the water table. Could this potentially be a problem with underpass/tunnel options further south (Regency Road, Torrens Road, Port Road, grange road) ?

i was thinking about this just yesterday

With the Anzac/South Rd underpass, where does the rain water go? presumably the depth of the underpass is greater than the depth of storm water piping? is pumping used as a solution?

Into a sump, to be pumped out...

[drsmith]

That image suggests the water table was not a problem for the Anzac Highway underpass.

[AG]

A high water table shouldn't be problematic for an underpass if it is designed properly. It just means designing the retaining walls on each side to keep the soils and groundwater from seeping into the underpass, and designing a proper drainage (and maybe pumping) system to clear out water that does end up in the underpass. Take a look at what happens to the Goodwood Road underpass at Millswood during heavy downpours for an example of poor drainage.

[drsmith]

A high water table shouldn't be problematic for an underpass if it is designed properly. It just means designing the retaining walls on each side to keep the soils and groundwater from seeping into the underpass, and designing a proper drainage (and maybe pumping) system to clear out water that does end up in the underpass.

There would obviously be an additional cost to this so perhaps it was just one factor that tipped the balance in favour of the viaduct rather than a critical failing for a tunnel/underpasses.

Given the cost of the superway would anyone like to hazard an estimate of how much to upgrade the entire route from the Port River Expressway to the Southern Expressway and compare it to widening to 6 lanes (3 each way) from Regency Road to Daws Road with grade seperation at Sturt Road, Sir Donald Bradman Drive and the Grange Road/Port Road/Outer Harbour Railway area.

[Aidan]

According to Superway Project Impact report (Alternative Designs Considered) the alignment of the north-south corridor south of Regency Road is still yet to be decided so it does appear that the southern end of the superway has indeed not been planned with a specific connection option in mind further south.

That's interesting, but moving it further E is just as likely as moving it further W, and the existing route is still the best candidate.

With an underpass at Regency Road surely some solution would have to be found to seperate local traffic from through traffic south of Regency road otherwise the local traffic there would find it very difficult to enter the roadway against a constant flow of traffic from the north.

Traffic would need to merge, but that's no different to the existing situation further S where traffic joining South Road merges with the traffic coming through the Gallipoli Underpass.

What alternatives are there in the absence of a new corridor for through traffic south of Regency Road (viaduct, tunnel or otherwise new alignment) ?

There are two other nonstop options: firstly making some minor improvements to South Road (installing a proper median and ensuring all lanes are 3.5m wide) and grade separating some of the side streets that currently join South Road). Secondly they could do all that and widen the road to 3+3 lanes as well.

An extra pair of lanes would be expensive, though nowhere near as expensive as a tunnel. But is it really needed? Even S of Anzac Highway I wouldn't rate an extra lane as a priority, and the northern suburbs have a lot more arterial roads than the southern suburbs.

Interestingly too, one of the reasons underpasses were not chosen along the superway route was because of the water table.

A very minor reason! A far more important reason is that it's an industrial area so there's no great disadvantage in going with an overpass, which is a cheaper option regardless of the water table.

Could this potentially be a problem with underpass/tunnel options further south (Regency Road, Torrens Road, Port Road, grange road) ?

'Tis something that will have to be factored into the cost, but it's not a technical obstacle.

[Shuz]

Should just make a note of it - with the release of the Property Council's Adelaide 2036 plan today, so far the voting indicates strong support for the establishment of a north-south freeway in this timeframe. Government may do just more than "do up" South Road?

[AtD]

It's an Adelaide Now poll. I'm suprised "No fat chicks" wasn't an option.

[fabricator]

I agree with AtD, if "Free Beer" were an option in the poll it would have won by a huge margin.

[drsmith]

That's interesting, but moving it further E is just as likely as moving it further W, and the existing route is still the best candidate.

Widening to the east south of Regency road could have the effect of removing individual property access southbound thus making that section of road more controlled access possibly up to the next set of traffic lights. Conflict between a constant flow of traffic from the north through an underpass of Regency therefore would not be in conflict with local access immediately to the south.

Traffic would need to merge, but that's no different to the existing situation further S where traffic joining South Road merges with the traffic coming through the Gallipoli Underpass.

The kind of local access I'm thinking of is from small side streets or individual properties (whether that be private or business) where there is no merging prospect at speed. While the Gallipoli Underpass is free flowing under Anzac Highway there are traffic signals upstream in both directions which would to some extent still allow for gaps between groups of vehicles for this local traffic to enter without having to merge.

There are two other nonstop options: firstly making some minor improvements to South Road (installing a proper median and ensuring all lanes are 3.5m wide) and grade separating some of the side streets that currently join South Road). Secondly they could do all that and widen the road to 3+3 lanes as well.

An extra pair of lanes would be expensive, though nowhere near as expensive as a tunnel. But is it really needed? Even S of Anzac Highway I wouldn't rate an extra lane as a priority, and the northern suburbs have a lot more arterial roads than the southern suburbs.

If some sections don't warrant widening to 6 lanes then all the better.

A very minor reason! A far more important reason is that it's an industrial area so there's no great disadvantage in going with an overpass, which is a cheaper option regardless of the water table.

'Tis something that will have to be factored into the cost, but it's not a technical obstacle.

I'm still trying to come to grips with the cost of a free-flowing expressway. If there is almost no change from $1bn for 4.8km then the whole route from the Port River Expressway to Darlington is going to be $5bn, perhaps much more. The cost may be so great that Adelaide's urban expansion may need to be planned around the full length of South Road never becoming a free flowing expressway.

[DM8]

I'm still trying to come to grips with the cost of a free-flowing expressway. If there is almost no change from $1bn for 4.8km then the whole route from the Port River Expressway to Darlington is going to be $5bn, perhaps much more. The cost may be so great that Adelaide's urban expansion may need to be planned around the full length of South Road never becoming a free flowing expressway.

I'm still trying to come to grips with the real possibility that the full length of South Road will never become a free flowing expressway in my lifetime. Land aquisition is a bitch - so many residential and commercial buildings built right up to the edge of the existing road. Not only is it going to require truckloads of cash, but also requires political balls and leadership - something which unfortunately hasn't been seen in this state for decades.

[muzzamo]

I'm still trying to come to grips with the real possibility that the full length of South Road will never become a free flowing expressway in my lifetime. Land aquisition is a bitch - so many residential and commercial buildings built right up to the edge of the existing road. Not only is it going to require truckloads of cash, but also requires political balls and leadership - something which unfortunately hasn't been seen in this state for decades.

Mention the word "toll" and the economics of it becomes quite different. Give it another 5 years or so and South, Goodwood and Marion Roads will be in gridlock. People will have no choice but to pay $3-$5 every time they drive on it in order to finance the project (not to mention providing a price incentive for only those that need to use the multibillion dollar road in peak hour to do so)

I think Sydney has at least 10 suburban freeway tunnels now.

[DM8]

I think Sydney has at least 10 suburban freeway tunnels now.

Sounds about right (some are rather short, might be debates coming up about which are tunnels and which are underpasses)

However, as I understand it, Sydney's terrain is far better for tunnelling and shoving things underground - it's all rock and hard ground. The Adelaide "Plain" is just that - very flat, and not far above the water table, plus it's mostly clay. Tunnelling is possible, but much more expensive to build and maintain.

Who knows what a road tunnel on the Adelaide Plain would do to the water table. The situation in Perth with the Graham Farmer Freeway tunnel and the north block of the Royal Perth Hospital comes to mind - the lowest two floors of the north block are full of water since the tunnel was built, as it raised the water table around it, and they couldn't pump the water out fast enough.

I recall Pat Conlon saying that he will not support tolls on SA roads. But pollies can change their minds (e.g. Melbourne's Eastlink).