[U/C] M2 North-South Motorway

[TorrensSA]

Yes I know this, I was just brainstorming, the real issue is removing 1000+ people from an area that really should be growing. It's only 2.5km out of the entire South Road that deserves a tunnel, it's so close to the city, a trench would effectively cut off the Western Suburbs from the city. I don't think it's justified to destroy the inner west for this. If this corridor was Portrush Road instead and it was around Norwood there would be no way a trench would happen, it's classist to destroy one areas heritage. A tunnel requires more money and more maintenance, but it also leaves prime real estate less than a km from the city available for housing.

[Nort]

As I live in the inner-west I'm trying to not have too much of an opinion on the tunnel debate to avoid any NIMBYism (far enough away from South Road that we wouldn't be effected either way other than how the trip into town looks afterwards).

I don't know about the feasibility of cut and cover. How long would it take to do? The current approaches have kept South Road open to traffic, even if slowed down. Cut and cover would seem to require shutting that section entirely and diverting traffic a long way around.

[Spotto]

I don't know about the feasibility of cut and cover. How long would it take to do? The current approaches have kept South Road open to traffic, even if slowed down. Cut and cover would seem to require shutting that section entirely and diverting traffic a long way around.

If cut-and-cover were to happen at HBR, the main issue would be diverting South Road traffic since that section would need to be completely closed (red). I guess it would be possible to close the Hindmarsh end of T2T and turn the Port Road ramps into the main entry/exit point, then direct South Road traffic along Port Road and JCD, effectively closing South Road as a main thoroughfare between Grange/Port Roads and SDBD except for local traffic (orange). Upgrades at Marion Rd/Holbrooks Rd/East Ave to realign the intersections would help turn it into a secondary north-south route and would be long overdue future-proofing upgrades.

For HBR, it might be possible to keep it open in a similar way to the bridge construction at Darlington and T2T; temporarily realign the road to build underneath HBR, then when it's finished move the road back and continue building the rest. A couple of businesses on the south side would be affected but there isn't a better option for this circumstance.

Naturally people will complain that their commute times are slightly longer and "how dare they be inconvenienced" regardless of what solution is devised for the rest of South Road, but it's short term pain for long term gain. Driving through the road works at Darlington was frustrating at times, but now that it's mostly finished it's brilliant.

[bits]

The hbr intersection is 7 lanes as it stands with a fair bit of space everywhere.
You only need 2 lanes of through traffic in each directions.
Which to me means you could do the cut and cover in 2 halves.

[Nort]

The hbr intersection is 7 lanes as it stands with a fair bit of space everywhere.
You only need 2 lanes of through traffic in each directions.
Which to me means you could do the cut and cover in 2 halves.

Could, but then you're looking at taking much longer and more expense since I imagine they'd have to reinforce the cut side to avoid it collapsing in from all the traffic next to it, then remove all that reinforcing structure.

Edit: actually, I was imagining it being one open road underneath, of course it would be more like two tunnels in opposite directions.

[dbl96]

500 houses at $500K = $250M.

Exactly $250m is dirt cheap compared to tunnelling that distance.
Much cheaper and easier to just buy the land.

Not only will it be cheaper and less risky upfront it will much cheaper and less risky for the life of the road, aka forever.

Precisely. Tunnels, especially bored ones, will also be expensive to maintain in the long term.

I think people are getting a bit carried away with the sexy idea of bored tunnels. They really aren't necessary in Adelaide. We can achieve the same result with more mundane but cheaper solutions.

Cut and cover is entirely possible. Most of the New York Subway and Paris Metro were built using cut and cover. China's current massive expansion of metro systems has been mostly cut-and-cover, in vastly more populated cities than Adelaide, with vastly more congested roads. Its all about how its managed.

Tunnel boring machines are necessary in a place like Sydney, where there is complicated topography, and chaotic, winding surface roads. Boring is also suited to Sydney's geology - there is rock just below the surface. In contrast, the Adelaide plain is soft clay. The Adelaide plain is also flat, and South Road is straight - this makes simply digging a trench and covering it over fairly simple.

People in Adelaide (and Australia in general) are often quite unimaginative when it comes to infrastructure. We just ape whatever they are doing in the big east coast capitals, and Australia as a whole tends to blindly follow the UK and US. If we looked more often for ideas beyond Sydney, and, more broadly, beyond the English speaking world, we would discover many superior solutions that we are currently ignorant to. Cut and cover is one such idea.

[AG]

I can't remember where I saw this, but I have seen some unique grade separation projects which involve putting traffic in one direction through a cut and cover tunnel, and then putting traffic in the opposite direction on an overpass which sits directly on top of and is supported by the tunnel structure, with the ramps to ground level at each end staggered to save ground level space.

[Saltwater]

A double-decker cut & cover tunnel might work, but I expect will still require the removal of at least one side of houses & businesses along South Road. Any other cut & cover or trench model would likely involve at least both sides along South Road, and all the noise that would create among local residents (I'm one of them very close to South Road) and businesses in the inner west.

[Eurostar]

No pain no gain, SA Governments can't keep putting it off

[claybro]

A double-decker cut & cover tunnel might work, but I expect will still require the removal of at least one side of houses & businesses along South Road. Any other cut & cover or trench model would likely involve at least both sides along South Road, and all the noise that would create among local residents (I'm one of them very close to South Road) and businesses in the inner west.

Well rest assured, if a trench is the preferred option, those of you who live "very close" to South road will notice s decrease in noise as the main carriageway is lowered. Beats me why the state should contemplate a tunnel, so that people who have chosen to live near an already polluted noisy major arterial, under a busy flight path, should hear no traffic noise.

[Saltwater]

Personally I think a trench through the inner west (the 5031 postcode at least) is unlikely. It would wipe out hundreds of 100+ year old houses and decimate the character of the area. Imagine the opposition if a similar plan was suggested near Parkside, Norwood, or North Adelaide (which is also directly under the flight path). So the question to me again comes back to how they funnel from the Hindmarsh to James Congdon Drive / SDB intersection

[Norman]

A double-decker cut & cover tunnel might work, but I expect will still require the removal of at least one side of houses & businesses along South Road. Any other cut & cover or trench model would likely involve at least both sides along South Road, and all the noise that would create among local residents (I'm one of them very close to South Road) and businesses in the inner west.

Well rest assured, if a trench is the preferred option, those of you who live "very close" to South road will notice s decrease in noise as the main carriageway is lowered. Beats me why the state should contemplate a tunnel, so that people who have chosen to live near an already polluted noisy major arterial, under a busy flight path, should hear no traffic noise.

In this context I don't think that's a good argument. Just because you live in a "shit" area now shouldn't mean the area should always be "shit". If the benefits of a tunnel are big enough to justify the cost a tunnel, then this will be a great opportunity to uplift the area and provide better living conditions, and maybe even get some higher densities going in the surrounding area.

[rev]

A double-decker cut & cover tunnel might work, but I expect will still require the removal of at least one side of houses & businesses along South Road. Any other cut & cover or trench model would likely involve at least both sides along South Road, and all the noise that would create among local residents (I'm one of them very close to South Road) and businesses in the inner west.

Well rest assured, if a trench is the preferred option, those of you who live "very close" to South road will notice s decrease in noise as the main carriageway is lowered. Beats me why the state should contemplate a tunnel, so that people who have chosen to live near an already polluted noisy major arterial, under a busy flight path, should hear no traffic noise.

In this context I don't think that's a good argument. Just because you live in a "shit" area now shouldn't mean the area should always be "shit". If the benefits of a tunnel are big enough to justify the cost a tunnel, then this will be a great opportunity to uplift the area and provide better living conditions, and maybe even get some higher densities going in the surrounding area.

I think the gist of it is that you live in an area with the states busiest road nearby and under a flight path, so construction noise will be a small price to pay for a short period if it means that a trench (or tunnel) will result in less traffic noise from the busiest road in the state.

With the lowered motorway, could they add sections of essentially canopies with vegetation on top? Perhaps near the intersections/bridges and any long open stretches of trench?
If you look at the current T2T lowered motorway, it's a bit barren in general, not very appealing and wouldn't do much for the surrounding residential area. I mean here we are talking about not destroying the character of Thebarton and so on, but we forget that a short walk away an entire row of homes and some businesses were demolished for the trench.

[Spotto]

If you look at the current T2T lowered motorway, it's a bit barren in general, not very appealing and wouldn't do much for the surrounding residential area. I mean here we are talking about not destroying the character of Thebarton and so on, but we forget that a short walk away an entire row of homes and some businesses were demolished for the trench.

The original concept design for T2T before it was extended to Pym Street was quite creative. Between Grange Road and Port Road, the northbound surface road crossed over to the same side as the southbound road; so instead of the two surface roads separated by the motorway trench, the trench was on one side and the surface road was on the other. Since that crossover would've been so short it might not have been worth the trouble, but since the remaining section of South Road will be much longer than T2T it might be more feasible. Would also avoid the Darlington (and Gallipoli Underpass) problem of intersections with major roads being separated across the trench with stopping in the middle; the crossover would keep it as one single intersection, unless they use cut-and-cover which would also solve the problem.

Original concept: https://www.youtube.com/watch?v=7Z6MMz-buN4

[SBD]

If you look at the current T2T lowered motorway, it's a bit barren in general, not very appealing and wouldn't do much for the surrounding residential area. I mean here we are talking about not destroying the character of Thebarton and so on, but we forget that a short walk away an entire row of homes and some businesses were demolished for the trench.

The original concept design for T2T before it was extended to Pym Street was quite creative. Between Grange Road and Port Road, the northbound surface road crossed over to the same side as the southbound road; so instead of the two surface roads separated by the motorway trench, the trench was on one side and the surface road was on the other. Since that crossover would've been so short it might not have been worth the trouble, but since the remaining section of South Road will be much longer than T2T it might be more feasible. Would also avoid the Darlington (and Gallipoli Underpass) problem of intersections with major roads being separated across the trench with stopping in the middle; the crossover would keep it as one single intersection, unless they use cut-and-cover which would also solve the problem.

Original concept: https://www.youtube.com/watch?v=7Z6MMz-buN4

The Weatherill/Mullighan (it seems to no longer be "Labor") plan had "short tunnels", presumably cut-and-cover, at each of Henley Beach Road and Sir Donald Bradman Drive. Motorway entrance/exits were decoupled from the crossing roads, as is done in other countries with express motorways parallel to other highways. When you get close to the turnoff you want, you get off of the motorway onto the "surface road", separately from making the turn.

The plan south of the Galipolli Underpass was to be an elevated motorway like the Superway through Wingfield. I assume that requires a narrower corridor than is required by a T2T-like trench. I have no idea what the noise effects are in the area, particularly a street or four away from it.