The release of the CRL designation documents has definitely helped clarify a few key facts surrounding the CRL. One of the biggest happens to be that the Inner West Interchange (IWI) has been dropped in favour of the Eastern link and that was picked up by the Herald yesterday. With that interchange gone it should mean AT can now hopefully start to put a bit of effort into what service pattern we can expect to see. I think that if they get that right, it is something they should be able to start using to help promote the project. It would help to show that the it isn’t about looping trains around and around in circles or just about improving access to the city centre but that by routing trains through the tunnel that we can open up new destinations.
First for the sake of comparison, here is my understanding as to the thinking was with the IWI. It was largely driven by the fact that the majority of passengers in the city centre would be going to either Aotea or Britomart so the focus was on getting them to those destinations first. That means sending all trains from the southern and eastern lines through to Britomart and then up the tunnel on to Aotea and eventually the IWI. Eastern line trains would then head out west to Swanson while Southern and Onehunga line trains would terminate at the the IWI. They would then have to travel back down the CRL, likely mostly empty before either going to a stabling yard to be built at the strand or back out to Onehunga or Papakura. Off peak a shuttle would run between the IWI and Newmarket however during the peak it would be extended to Henderson. Just to make things even more confusing there would also be a handful of trains from the west at peak times that would do one run then terminate at Britomart before going to the previously mentioned strand stabling depot. For the sake of making it easier to show, I have shown this without special peak services.
So what can we do now that we know the eastern link instead of the IWI is being designated. By sending the Onehunga trains via Grafton it then gives us two routes that enter at the southern end and two at the northern end. Linking then together so they don’t end up going back on themselves means the western and southern lines get joined while the eastern and Onehunga form the second line. People from the west who want to get to Newmarket would still be able to do so either be staying on the train or swapping at the new Newton station like described in this post. Any trains that are not needed off peak would likely finish their run out to the suburbs before heading to a nearby stabling depot (there are now a number which fairly close to end of each of the major lines).
Going a step further, I think the next rail project off the rank shouldn’t be rail to the airport but the comparatively cheep branch line to Mt Roskill. The reason for this is that the route is all ready designated (was done in the 1940s) while the more recent motorway works have included providing for the line at most places. With the exception of Dominion Rd, all bridges have a clear space or extra span for the rail corridor so the line should be fairly easy to build. It may not seen that important but the route ends up serving a couple of useful purposes. Stations at Dominion Rd and Stoddard Rd could serve as a focal point for the local buses from the southern end of the isthmus. That should either help free them up for their run to the city and/or allow the number of buses that need to run all the way to the city centre to be reduced. The other big benefit would be that services that run on this branch would add capacity on the inner parts of the Western line at the parts it is usually at its busiest and the area most likely to benefit from the CRL due to the vastly reduced time to the city centre.
The question of course is where you would run this line to and when you think about other major PT developments that are going on, and you instantly turn to Panmure. With the AMETI busway feeding into the Panmure station having extra capacity, and frequency is probably going to be extremely useful. A turn back station at Panmure (or possibly Sylvia Park) which is just used by the driver to change ends, would allow those trains to terminate here without getting in the way of other trains using the tracks.
What we end up with is a network with three main lines going West, East and South and with a series of short lines that work to boost capacity on the inner parts of the network. The Mt Roskill branch would also allow us to look at other through routing options but I won’t explore that further in this post.