Problems with the M4 East and Strathfield Metro

Posted: October 24, 2012 in Transport
Tags: , , , , , ,

When I discussed the main problems I had with Infrastructure NSW’s First Things First report, I mentioned that there were a few other issues I had with it which I had left out for the purposes of brevity. Those two were the potential for high density development along the Parramatta Road corridor and the problems caused by trying to retrofit the Harbour Crossing into a single deck metro system.

The cut and cover slot construction method proposed for the M4 East benefits from having much lower costs than a tunnel. The concept art for this shows an increase in housing density along a rejuvenated Parramatta Road (below). Suggestions for increasing housing density along Parramatta Road have been talked about for decades, and the corridor has been spoken of as being able to house some 100,000 residents. But high density needs good quality public transport to work (a motorway is not enough), just as good quality public transport needs high density to work. And what this proposal seems to be lacking is improved public transport, either Bus Rapid Transit or Light Rail, perhaps even an underground or aboveground metro, to carry large quantities of people along the corridor.

An artists impression of the M4 East portion of West Connex. Click on image for higher resolution. (Source: First Things First, page 89.)

The Urban Taskforce is one group pushing for higher densities along Parramatta Road and its CEO, Chris Johnson, voiced his concerns for just this reason. This means one of two things: the opportunity for high density, walkable, sustainable housing will be squandered, or provision must be made for some kind of mass transit system to be built concurrently with the M4 East.

Infrastructure NSW’s insistence that a Second Harbour Crossing it too expensive and should be deferred until it is really needed also has its problems. One would be that the CBD rail lines could be shut down for months and access remain restricted for years as the existing Harbour Crossing is converted to single deck metro capability and then connected to lines that enter the CBD from the South. Such a conversion and link would also occur with a Second Harbour Crossing, but this would involve a new line built through the CBD which ensures that any lost capacity is made up by new capacity through this new line.

What the Infrastructure NSW report does not seem to appreciate is the complicated system of connections between different lines. Connecting trains on one line to another can often result in the use of flat junctions, which delay trains on other lines. Think of it like an intersection with traffic lights, if there is a green light for one road then there must be a red light for the other road. This is why there is a system of dives and flyovers on the rail lines between Redfern and Central, to allow trains to move from one line to another without disrupting trains on those other lines. But these connections are limited in what they can do, and to build in new ones to link up the lines the way Infrastructure NSW wants would result in the shut down mentioned earlier.

Taking the massive disruptions into account, along with the cost of retrofitting the existing crossing, and the lack of long term capacity improvements that it brings, you have to start to wonder if not building a Second Harbour Crossing really is as unaffordable as Infrastructure NSW makes it out to be.

  1. cudchewer says:

    Several points here.

    Infrastructure NSW makes the comment that capacity can be doubled on existing rail lines using better signalling and so on. I think this is fair comment and I’ve yet to see this taken on and discussed fully.

    A few years ago there was a proposal to fit a rail line within the structure under the deck of the Harbour Bridge. And a plea was made to have this proposal properly assessed. It certainly appears to be a plausible idea. Why has the idea been completely forgotten? In the proposal, the new rail line would project about 1.5 metres below the deck structure. Would this figure be smaller if the line were dedicated to single deck traffic?

    Why is no-one taking another look at the cost of tunneling and reconsidering whether tunneling specifically in Sydney sandstone could not be done more cost effectively? Its tunneling costs that seems to be the root cause of many of Sydney’s transport problems but it doesn’t seem to get serious attention. Why? Look at how it motivates Infrastructure NSW to avoid a tunnel for the M4.

    Speaking of the M4 east. There are alternate engineering approaches to this problem that don’t appear to have been given consideration. And this is quite apart from tunneling.

    One approach is to use Parramatta Road but essentially replace it with a long bridge. An equivalent structure would be the new flood plain bridge at Kempsey.

    Another approach is essentially another take on the above. Instead of conventional columns and the girders, you could use prefab concrete sections – not unlike a large culvert.

    Both approaches would leave an unbroken surface at normal ground level. And on top of that you then have the space to provide proper public transport.

    Both of these approaches have the potential to actually save money, by simplifying and speeding up the construction, and neither would have the cost of a tunnel.

    But how come they haven’t been considered? And is there a chance that if the M4 east gets to RMS, someone there might have the initiative and imagination to consider these options?

    Incidentally I agree that Parramatta Road is an ideal opportunity to both have denser housing and to design in public transport from the start, but the “slotted” idea physically works against that.

  2. The idea of a Harbour Rail crossing hung underneath the Harbour Bridge was discussed here and here:

    You’re spot on with the cost of tunneling being the problem. If you look at recent toll roads built in the last 20 years or so, those that have been entirely tunnels (Cross City Tunnel and Lane Cove Tunnel) have gone into receivership, while those that have been entirely surface (M2 and M7) have been financial successes. The M4 East proposal is more like the Eastern Distributor, which is in between.

  3. cudchewer says:

    I guess what I’m asking is, why is the idea of hanging rail lines under the Harbour Bridge not being considered by the powers-that-be?

    My point about tunneling is that we could potentially build cheaper tunnels and that that would have a huge difference not just on projects like the M4 east but on the feasibility of rail projects and high speed rail as well.

  4. moonetau says:

    A better option would be to “hang” two car lanes under (actually inside the structure) of the bridge, if it was felt that they were needed. As would be the case if the rail lines on the eastern side of the bridge were restored, thence to Wynyard platforms 1 and 2 etc.
    A much cheaper way to create the second crossing.

  5. cudchewer says:

    That’s actually not a bad idea. I wonder how it would work in terms of the spaghetti at the end of the bridge?

  6. moonetau says:

    The reinstated rail bridge carrying trains from Nth Sydney station would go to where the toll booths are now. The new car lanes would enter a tunnel here and go under lanes 1-6, exiting the abutment and joining the substructure of the bridge. At the southern end they would go through the other abutment under the four rail lines (which start to converge as they get closer to Wynyard) and then exit up and to the left of what is now the off ramp to the Cahill expressway.
    Much easier than hanging two rail lines (SMH and Glazebrook recommended these) as would only need vertical space of say 3 m as opposed to 6 or more with rail. Cars can negotiate curves and gradients more easily than trains.
    Short term solution until we can get rid of the Cahill Expressway.
    ™ You read it here first!!😊

  7. moonetau says:

    Here is a picture which may be of interest:

  8. cudchewer says:

    Ok, still thinking about that..

    How many car lanes could you fit under the bridge? The plan for rail suggested 2 with maybe more later. But when you actually look at the bridge from underneath, its clear why more than 2 lanes would be trickier..

  9. cudchewer says:

    Yep, I’m aware of the older bridge there. What I can’t recall is why they chose to have those other two rail lines on the other side of the bridge. Half remember the original plan was to go to the northern beaches?

  10. cudchewer says:

    Ok.. have thought that one through. Seems workable though a bit messy on the southern end. You’d have to come up with a plan that minimises traffic disruption while you’re at it.

  11. Peter Isaacs says:

    Two tracks of trains carry the equivalent of 10 lanes of motor car traffic so by running trains to Wynyard and back over the Eastern 2 lanes of the Harbour bridge one is effectivly adding 8 car lanes to it’s capacity. Worried about turning all those trains back? The Eastern Suburbs line is designed to turn back 20 trains per hour. Wynyard is not exactly the same configuration but an in tunnel crossover before Wynyard would allow close to that 20. That would be a significant increase in capacity without going any further south and as well the tunnelling costs would be zero.

  12. moonetau says:

    There is a stub tunnel south of Wynyard station which was used to turn back / store the trams. Not sure if it is long enough to accommodate 160m long trains though.
    I’m not in favour of adding two car lanes underneath.
    As you point out Peter extra rail lines would be much more cost effective.
    But imagine the reaction from the NRMA and Nick Greiner’s INSW!!

  13. cudchewer says:

    You’re not going to get more train lines on the bridge without compensating car lanes. To my mind, adding the car lanes under the bridge makes most sense because they need the least vertical space.

  14. […] Problems with the M4 East and Strathfield Metro […]

  15. […] Problems with the M4 East and Strathfield Metro 24 October 2012 (15 comments) […]

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