Unclogging Adelaide’s north-south road corridor: Mk I

Since 2005, there’s been an increasing push for improvements to the flow of traffic in the north-south direction through urban Adelaide. In a metropolis pushing outwards to the north and south from the city, only one road corridor spans the entire north-south length through Adelaide – South Road – arguably also the city’s most congested road corridor.

Several projects have been built or are under way in order to keep South Road moving and keep the main spine of Adelaide in healthy condition. In 2009, the Gallipoli Underpass of South Road at Anzac Highway was completed forming the 2nd grade separated intersection on South Road after the Emerson Crossing a couple of kilometres to the south. In early 2010, the tram line between Gallipoli Underpass and Emerson Crossing was also grade separated, creating approximately 4 kilometres of intersection-free road between Edwardstown and Everard Park.

Map showing section of South Road discussed in this post and of projects taking place along Adelaide's north-south corridor as at February 2011 (Source: DTEI)

At the south end of South Road, the Southern Expressway will soon commence its duplication into a dual carriageway freeway standard road (Yes, that’s right! The road only has one carriageway with the traffic direction depending on time of day!). At the Darlington end of the expressway – the end closer to the city – an interchange and underpass of Sturt Road will provide a smoother transition between the expressway and Main South Road.

At the north end of South Road, several projects forming a new north-south corridor have been constructed, are under construction or are in planning. The most recently opened road was the Northern Expressway in late 2010, which forms the northernmost section of the north-south corridor and providing a key link bypassing the northern suburbs to the Barossa Valley. Currently in planning is the Northern Connector which is the southern continuation of where the Northern Expressway currently terminates at Port Wakefield Road through to the northern end of South Road at Wingfield. Finally, the South Road Superway is currently under construction as a 2.8 kilometre long elevated roadway between Wingfield and Regency Park.

Even with all the projects completed, in planning or with construction under way, there’s still large gaps to be dealt with from Regency Park to Everard Park and Edwardstown to Clovelly Park. South Road through Ridleyton between Port Road and Torrens Road is particularly notorious for traffic congestion and accidents as this is the narrowest section of the corridor with barely enough room for 4 lanes (2 each way), no median or dedicated turning lanes. In an accident on November 22 2010, a truck on the outermost lane clipped a power pole adjacent to the kerb causing power lines to fall on the road resulting in area wide traffic delays for the following day and thousands of nearby properties to go without power. So far, little action has been taken to improve traffic flow on either of these long sections of South Road. A 600 metre long tunnel from Hindmarsh to Croydon under Grange and Port Roads was proposed by the South Australian Government in 2005, but this plan did not eventuate.

The sections of South Road that have not yet been planned for upgrade are also some of the most difficult as they run through the well built-up areas along the north-south route. The projects at the southern and northern ends of the road are in open areas with low density and have had funding assistance from the Federal Government. To build extensive overpasses and elevated roads along the existing South Road would result in noise and privacy issues to properties near the road. Widening the road along its length would require a very large number of property acquisitions. Also, building individual underpasses and short tunnels can eliminate intersections but result in congestion further along the road as experienced following the completion of the Gallipoli Underpass with traffic congestion moving south to Castle Plaza and Edwardstown.

This leaves a long tunnel as an option to bypassing South Road altogether. Building a twin-tunnel between Regency Park and Clovelly Park would require tunnels over 20 kilometres long, which an impractical and extremely expensive solution. However, building two shorter tunnels is possible making use of the existing Gallipoli Underpass and Emerson Crossing along its route, but these tunnels would still be amongst the longest in Australia. Discussed here is the northern of the two twin-tunnels, between Regency Park and Thebarton.

Much of the focus of improving South Road so far has been along the road itself, but this ignores the real issue of providing better north-south access by only focusing on the one road corridor. Near the city, a perfectly good and underused road corridor called James Congdon Drive through Mile End provides a possible solution to providing a new north-south route. This could be upgraded to a freeway standard road by upgrading the access points along the road, moving the cycle paths, widening the road to three lanes in each direction and providing overpasses over Railway Terrace, Sir Donald Bradman Drive and where it rejoins South Road to provide a smooth transition as highlighted by the purple lines on the diagram below. Overpasses and/or underpasses at the two intersections between James Congdon Drive and the Gallipoli Underpass would eventually need to be constructed as well.

Stage 1 for improving north-south access: Upgrade James Congdon Drive to freeway standard and a tunnel from Thebarton to Regency Park.

The real challenge to the plan is building the long twin tunnels – marked in green on the map above – from James Congdon Drive at Thebarton to the south end of the currently under construction South Road Superway at Regency Park. These tunnels – with side entrances and exits at Torrens Road and Port Road at the north and south ends respectively – would be over 6 kilometres in length and have two lanes for each direction. This would avoid the need for extensive property acquistions, minimise delays on South Road due to construction work and remove traffic from many suburban streets – assuming commuters don’t face an overpriced toll to use the tunnel. By comparison, the Heysen Tunnels in the Adelaide Hills are only 450 metres long. Even at 6 kilometres long, these would not the longest tunnels in Australia. That title goes to Brisbane’s Airport Link tunnel project, where the twin tunnels currently under construction will be 6.8 kilometres long when complete in 2012.

The twin tunnels would allow traffic to bypass an 8 kilometre section of South Road, and also allow trips from the city all the way to the Barossa Valley and Port Wakefield Road without passing a single traffic signal except in the central business district – assuming the Northern Connector is built as well. It would also speed up trips between Adelaide Airport and the northern suburbs, with only five signalised intersections between the airport and the freeway entrance at James Congdon Drive traveling via Sir Donald Bradman Drive.

There’s many challenges involved with a project this large. The biggest technical challenge involves finding the most suitable alignment for the tunnels that runs through appropriate geological conditions – information as an individual that I don’t have – and one that avoids building foundations. Locations for vent shafts for the tunnels and finding community acceptance for them could also prove difficult.

These projects are not cheap either. The Airport Link Project, which is effectively three projects in one including a busway and upgrades to existing roads, is estimated to cost $4.8 billion to build under a public-private partnership (PPP). Building under a PPP has its own challenges as experienced by the consortium BrisConnections, who is building the project, with the value of its units listed on the Australian Stock Exchange dropping to 0.1c per unit, the lowest possible on the exchange and was almost wound up in 2009 amidst much controversy. The other major tunnel in Brisbane, the Clem7, has been facing difficulties of its own with traffic in the tunnel falling far short of projected figures and a lack of toll revenue. Getting the financial structure right could prove difficult as seen by the number of failures in PPPs on other tunnel projects in Sydney and Brisbane in recent years.

It should be noted that this is not an official proposal, it is merely an idea and vision for improving the flow of north-south traffic across metropolitan Adelaide taking existing projects into consideration. Discussion on dealing with traffic congestion on South Road around Castle Plaza and Edwardstown will be detailed in a later post.

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10 Responses to “Unclogging Adelaide’s north-south road corridor: Mk I”

  1. chris of brompton Says:

    Origin had two deep bores done for testing in Chief Street a few years ago. The local opinion is that it’s pug and gravel down to 130 feet. But the Para fault intersects your proposed tunnel anyway, so the going could be tricky however deep you go

    • Andrew Says:

      Hi there Chris,

      Do you know at which end of Chief Street were the bores drilled?

      Andrew

      • chris of brompton Says:

        They drilled just outside the old retort building, close by to the railway bridge. The crew told me they were going down 200m. It was a big rig.

      • Andrew Says:

        Since I published this post a few days ago, there has been another major accident on the dangerous section of South Road between Port and Torrens Road. Unfortunately, there were fatal injuries in this accident.

  2. Unclogging Adelaide’s north-south corridor: Mk II « Urban Rediscovery: Creating Better Communities Says:

    […] Adelaide’s north-south corridor: Mk II By Andrew In the previous part on Adelaide’s north-south corridor, I discussed an idea about upgrading James Congdon Drive to freeway standard and building a tunnel […]

  3. Tanya Stephen Says:

    I was hoping you could email me with the name of the company who are currently building are & responsible for the construction of the expressway at South, Regency Park?

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  6. Gloria Says:

    It’s hard to find well-informed people in this particular subject, however, you sound like you know what you’re talking about!
    Thanks

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