Summary of 4 track exploratory design near Middlemore Station
The Auckland Rail Programme Business Case (ARPBC) identified options to increase rail
capacity across the Auckland rail network. This included options for increasing the number of
tracks between Wiri and Westfield which would provide increasing levels of capacity, cost
and impacts.
Subsequent to the ARPBC, KiwiRail undertook an exploratory design exercise with the intent
to support subsequent business case phases; provide information on existing constraints;
identify issues and opportunities for further investigation and highlight insights to inform
planning of the business case phases.
An options assessment wil need to be undertaken during the subsequent business case
phases that considers safety, impacts to stakeholders and existing infrastructure and cost
effectiveness. It should be noted that the Middlemore section cannot be considered in
isolation as considerations north and south of the station would also need to be assessed
together with the Middlemore section in a future options assessment.
The exploratory phase considered an addition of a 4th track to the existing 3 track section of
the network through Middlemore, noting the 3rd track is located to the west of the existing
lines and construction of this is nearing completion. Investigation of more than 4 tracks
would be subject to further assessment in a future phase.
The following is a summary of the draft exploratory exercise for the section of the rail corridor
near Middlemore station.
1. Purpose/objective
To document the optioneering process for any emerging option(s) taken forward to the
business case and design phase.
2. Approach
The initial focus of the exploratory design has been to assess and compare options for
constructing the future additional mainline on the West, on the East, or one on each side
(Central).
3. Requirements
The exploratory design used the following requirements from the ARPBC:
• Four tracks, as two pairs of independent mainlines.
• Western mains are intended to carry freight, long-distance and inter-regional
passenger services, and express metro passenger trains.
• Eastern mains are intended for high frequency all stopping metro passenger trains.
• Under disrupted or maintenance mode all services must be able to use either pair of
mainlines.
• Al mains to preserve, or increase, existing line speed.
• No planned turnback movements anticipated.
• Platform length equivalent to 9 car EMUs, and preference for straight platforms.
• The preferred configuration is an island platform with two laterals, however two island
platforms may be considered subject to site constraints.
4. Existing Rail Infrastructure
• The 3rd main services a widened platform on the west side.
• OHLE, signalling and fibre / communications infrastructure.
• There is a grade separated pedestrian overpass located approx. in the middle of the
platforms with a lift, stairs and a walkway.
• There is another grade separated pedestrian crossing at the north end of the
platform.
5. Existing Non-Rail Infrastructure
• A 1200mm dia. wastewater pipeline runs parallel to and on the west side of the
existing up main adjacent Grey St south of the station.
• A large number of major underground utilities cross east to west and diagonally
across the rail corridor
• Numerous new retaining walls/structures have been constructed on the western side
of the rail corridor as part of the W2QP project.
• A number of overland flow paths are present through the area.
• The Hospital facilities include roads / roundabouts / parking etc adjacent the station.
6. 4th track options
The exploratory design considered options to the west, central and east. It was noted
that the influence of current and future property development either side of the
corridor is unknown.
West option
• The 4th main would be constructed to the west of the 3rd.
• A new lateral platform would be constructed to the west.
• The existing pedestrian footbridge would be impacted by the new track and platform
configuration.
Central option
• The recently constructed 3rd main would remain as built through the station platform
area but, south of the platform the 3rd main would be relocated further to the west
• The pedestrian overpass to the station platform would be impacted by the new track
and platform configuration and may require total replacement.
East option
• The East option is relatively the same as the Central option from a station platform
perspective however the track connections at either side of the platforms differ.
• The recently constructed 3rd main and the existing Up main would remain as built to
the north and south of the station platforms.
• The new East main would shift further east to provide separation to the existing
Down main track to the north and south of the station platforms.
• The existing eastern lateral platform would remain in place but be extended to the
north and widened to the east to create a two island platform configuration.
• The pedestrian overpass to the station platform (on both sides of the corridor) would
be impacted by the new track and platform configuration and may require total
replacement.
7. Maintenance Access
Consideration of maintenance access on foot and by vehicle has been considered in the
options with varying impacts to existing infrastructure and property.
8. Emerging findings
The exploratory analysis indicates the following:
• Future phases wil need to assess whether 4 or more tracks are required.
• The ultimate configuration wil influence the option that that is taken forward. For
example future options assessment may prefer an east option for a 4 track
configuration and a west option for a 6 track configuration.
• The level of maintenance access impacts scope.
• Al options have significant land impacts.
Document Outline
