Cross River Rail's Achilles Heel - Part 2 - Northside

BrizCommuter recently looked at capacity constraints on the Beenleigh Line that will hinder optimal use of Cross River Rail (CRR) and restrict future capacity enhancements. Whilst the constraints on the Southside are most critical in the short term, there are also similar capacity constraints on the Northside.

There are currently 4 tracks between Mayne (the large depot near Bowen Hills) and Northgate, with a track in each direction for the Mains and Suburbans. The Main tracks are used by the Caboolture, Sunshine Coast, and Redcliffe Peninsula Lines. The Suburban tracks are used by the Shorncliffe Line (with some services terminating at Northgate), Airport Line, Doomben Line, and with the Ferny Grove Line branching off at Bowen Hills.

4 Track Bottleneck

The problem is that CRR will join the Mains at Mayne, with no additional tracks added between this location and points further North. Thus the Mains North of Mayne (does that rhyme?) will be utilised by both via CRR services, and via existing CBD Line services. This is likely to be split equally, with 24tph worth of am peak Inbound/Southbound services being split into 12tph via CRR, and 12tph via existing CBD Line. The Mains North of Mayne will thus have a very poor capacity increase from the current 20tph to 24tph. This can actually be achieved alone just through new signalling (plus more trains and drivers), and doesn't actually require CRR to be constructed. Thus the lack of additional tracks on Brisbane's Northside makes for a very poor business case for CRR.

So what can be done to make better use of the $5b CRR tunnel? There is no question that to fully unlock CRR will require additional tracks on the Northside between Brisbane and Petrie (Lawnton to be precise). The most ideal solution would be to build the Trouts Road Line, which has been discussed in detail before on BrizCommuter's blog. This would ideally run in a tunnel from Roma Street (connected to CRR), surface at Everton Park, and run along the Trouts Road / North West Transportation corridor to Strathpine. A 4th track would be required between Strathpine and Lawnton. This would allow up to an additional 24tph to run to/from the Caboolture, Sunshine Coast, and Redcliffe Lines instead of a pathetic 4tph. It would speed up journey times from Brisbane to/from Caboolture and the Sunshine Coast, and also add stations to many Northern Brisbane suburbs that are currently devoid of decent public transport. Sadly, tunnel stubs to allow the Trouts Road Line to be easily connected to CRR were left out of the design, so to make this connection will require the closure of CRR for possibly a couple of months.

BrizCommuter's proposal for the Trouts Rd Line

A cheaper, but less effective version would be for the Trouts Road Line to join the Ferny Grove Line at Alderley. The tracks could be skewed around Mayne to re-route the Shorncliffe, Airport, and Doomben Lines onto the Mains. All Mains North of Mayne services would be routed via CRR. However this would have minimal journey time advantages due to the indirect nature of the inner-Ferny Grove Line, and only allow for an additional 16tph of services from Caboolture, Sunshine Coast, Redcliffe, and Ferny Grove Lines.

A final option would be to add additional tracks along the existing North Coast Line. However with the area between Mayne and Northgate already being quite built up, this would be almost impossible.

There is no question that in the current iteration, CRR is very poor value for money. It is imperative that funding is found to build the Trouts Road Line to allow for significant train service improvements from the North, and get much better value for money from the $5b spent on CRR.