Cross River Rail - Mayne Capacity Constraints

BrizCommuter has previously discussed the bottlenecks at both ends of Brisbane's Cross River Rail tunnel, and this post looks in more detail at changes to the Northern end where Cross River Rail (CRR) plugs into the rest of the rail network at Mayne (near Bowen Hills).

CRR adds 2 extra tracks (CRR Up and Down) for passenger services through Brisbane's CBD for a total of 6 tracks, however at the Northern end, those 2 tracks need to plug into the existing 4 tracks (Mains Up and Down, and Suburban Up and Down) just south of Albion. Concerningly, information on proposed rail operations is extremely limited on CRR's website. It is assumed that up to 24tph services will run on the existing Mains between Albion and Northgate. This will split into the Mains and CRR tracks at Mayne. For example 12tph am peak from Caboolture/Sunshine Coast will run via CRR, and 12tph am peak from Kippa-Ring will run via the Mains through the CBD. Due to this frequent peak service merging or splitting at this junction, it would be expected that a grade seperated junction would be provided at Mayne. Unfortunately, it seems that this is no longer the case.

The other problem with plugging 6 tracks into 4 (technically 4.33 if you include the Ferny Grove Line), means that CRR will not provide any capacity increase for train services to/from Brisbane's Northside. All of the service improvements will be due to implementing European Train Control System (ETCS) - Level 2 signalling, and not from spending over $5b on building a new tunnel. To increase Northside capacity, extra tracks will need to be constructed North of Brisbane, of which the Trouts Road Line / North West Transportation Corridor would be the most sensible option.

In Project Change Application 1 (2017), there was a grade seperated junction, with the Up CRR line running in a trench under the Up and Down Mains lines. Track layouts also placed stabling in-between the CRR Lines at Mayne, and Mains at Mayne North to reduce conflicts. This layout seemed quite logical, aside from lack of track connections between the Mains and Suburbans (on which the Airport/Doomben/Shorncliffe Line) services run on for operational flexibility.

Project Change 1 - Mayne

Project Change 1 - Mayne North

Then came along "cost cutting" Project Change 4 (2019). This removed the grade seperated junction, and replaced it with a track layout that seemed to defy any operational logic as it prevented the Down Mains at Bowen Hills (services from Ipswich/Springfield) from plugging into the Down CRR (at Albion). This may have been a major design mistake. Alternatively the operational plans may have been to run all 24tph services from Caboolture/Sunshine Coast/Kippa-Ring via CRR. However there is insufficient track capacity at CRR's Southern portal to allow this unless all Gold Coast/Beenleigh Line services are run via CRR, and none via South Bank.

Project Change 4 - Mayne

Project Change 4 - Mayne North

The most recent version is Project Change 7. This has no accompanying information in the Request for Project Change 7 documentation. This is operationally much better than the illogical Change 4 track layout, as it allows services from Up and Down Mains, and Up and Down CRR to merge into the Up and Down CRR/Mains near Albion. However, as junction this is not grade seperated, it is less likely that services will now be split at this junction. It also allows services from the Up and Down Mains to connect into the Up and Down Suburbans which allows for more operational options.

Project Change 7 - Mayne

Project Change 7 - Mayne North

The downside of the Project Change 7 track layout is that there is no grade seperation, between the merging or splitting CRR and Mains services (nor services being switched between the Suburbans and Mains). This means that a train service running from Ipswich/Springfield to Kippa-Ring via Central, will have conflicting movements with a train service running from Caboolture/Sunshine Coast to Gold Coast via CRR. Whilst this can be timetabled out, either train service running late will cause knock on operational issues to the rest of the network. Changes to track layouts should have sufficient merit to have publicly available documentation on why the changes have been made.

The bottleneck and track layout at Mayne raises a list of serious concerns:

• Why was the grade seperated junction at Mayne for Mains/CRR tracks removed from the plans?
• Why are the proposed rail operations for Cross River Rail being kept a secret? Surely this is one of the most crucial parts of a project that is designed to increase rail capacity?
• Why is there no mention of the track layout changes at Mayne in the Request for Project Change 7? Is the Coordinator-General even aware of these changes?
• What are the long term plans for connecting Cross River Rail to the Trouts Road Line / North West Transportation Corridor, and is this route safeguarded for rail transport?

Note: all screenshots from http://statedevelopment.qld.gov.au/coordinator-general/assessments-and-approvals/coordinated-projects/completed-projects/cross-river-rail-project/project-changes.html