Terrace Motorway Tunnel
Encyclopedia
The Terrace Tunnel
takes the Wellington Urban Motorway
(SH1)
under The Terrace in central Wellington
, New Zealand
. Opened in 1978, it is 460 metres in length.
during peak periods rush hour
. However flows at the southern end of the tunnel have improved somewhat since the opening of the Wellington Inner City Bypass
.
The tunnel is one of the few single-carriageway stretches of motorway in New Zealand. All that separates opposing flows of traffic is a set of double no-overtaking lines.
The tunnel was opened as part of the extension of the Wellington Urban Motorway through Thorndon to Te Aro and was originally envisaged to include a parallel three-lane tunnel exclusively for southbound traffic (with the existing tunnel built for northbound traffic only). The motorway was intended to be extended to Mount Victoria Tunnel
which would also have been duplicated.
However this proposal was shelved in the early 1970s as the rising cost of building the single tunnel ruled out duplication for the foreseeable future and the extension beyond Willis Street. The cut in funding sees the design of the motorway abruptly reduce from about the Bowen Street overbridge as six lanes are curtailed to three lanes. Appraisal of expected traffic flows also indicated that the second tunnel would not be needed for many years.
A reversible lane
(tidal flow) system as used on the Auckland Harbour Bridge
has been proposed. Investigation as part of the tunnel link project raised questions about safety of such an option, but it has not been ruled out. Some of the pillars for the second tunnel approaches are visible in the Clifton Terrace carpark adjacent to the cable car line, as is some of the approach road which currently forms part of the upper deck of the Clifton Terrace carpark. These pillars may also be seen on the left hand (eastern) side of the "Wellington Terrace Motorway, looking south" webcam on the CityLink website (http://citylink.co.nz/products/webcam/terrace-south/).
As you enter the tunnel it is impossible to see the other end, as it curves in the middle.
. From 2007 this is via the Wellington Inner City Bypass
.
Upgrade works are being completed by the Wellington Tunnels Alliance - formed by Leighton Contractors, SKM, Aecom and NZTA.
. The study indicates a cost of (NZ) $80 million for a second tunnel.
It has been proposed as of December 2009, that a second duplicate tunnel will be constructed within the next 10 years.
Tunnel
A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
takes the Wellington Urban Motorway
Wellington Urban Motorway
The Wellington Urban Motorway, part of SH 1, is the major road into and out of Wellington, New Zealand. It is 7 km long, ranges from three to six lanes wide, and extends from the base of the Ngauranga Gorge into the Wellington CBD....
(SH1)
State Highway 1 (New Zealand)
State Highway 1 is the longest and most significant road in the New Zealand roading network, running the length of both main islands. It appears on road maps as SH 1 and on road signs as a white number 1 on a red shield, but it has the official designations SH 1N in the North Island, SH 1S in the...
under The Terrace in central Wellington
Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. Opened in 1978, it is 460 metres in length.
Coordinates
- North portal: 41.2872°N 174.7717°W
- South portal: 41.2913°N 174.7718°W
Design
The tunnel has three traffic lanes, one southbound and two northbound. The merge towards single southbound lane causes frequent congestionTraffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...
during peak periods rush hour
Rush hour
A rush hour or peak hour is a part of the day during which traffic congestion on roads and crowding on public transport is at its highest. Normally, this happens twice a day—once in the morning and once in the evening, the times during when the most people commute...
. However flows at the southern end of the tunnel have improved somewhat since the opening of the Wellington Inner City Bypass
Wellington Inner City Bypass
The Wellington Inner City Bypass is a westbound one-way road varying from two to four lanes largely at ground level in central Wellington, New Zealand, part of State Highway 1, and was opened in March 2007....
.
The tunnel is one of the few single-carriageway stretches of motorway in New Zealand. All that separates opposing flows of traffic is a set of double no-overtaking lines.
The tunnel was opened as part of the extension of the Wellington Urban Motorway through Thorndon to Te Aro and was originally envisaged to include a parallel three-lane tunnel exclusively for southbound traffic (with the existing tunnel built for northbound traffic only). The motorway was intended to be extended to Mount Victoria Tunnel
Mount Victoria Tunnel
The Mount Victoria Tunnel in the New Zealand capital city of Wellington is 623 metres long and 5 metres in height, connecting Hataitai to the centre of Wellington and the suburb of Mount Victoria, under the mount of the same name...
which would also have been duplicated.
However this proposal was shelved in the early 1970s as the rising cost of building the single tunnel ruled out duplication for the foreseeable future and the extension beyond Willis Street. The cut in funding sees the design of the motorway abruptly reduce from about the Bowen Street overbridge as six lanes are curtailed to three lanes. Appraisal of expected traffic flows also indicated that the second tunnel would not be needed for many years.
A reversible lane
Reversible lane
A reversible lane , called a counterflow lane or contraflow lane in transport engineering nomenclature, is a lane in which traffic may travel in either direction, depending on certain conditions...
(tidal flow) system as used on the Auckland Harbour Bridge
Auckland Harbour Bridge
The Auckland Harbour Bridge is an eight-lane box truss motorway bridge over the Waitemata Harbour, joining St Marys Bay in Auckland with Northcote in North Shore City, New Zealand. The bridge is part of State Highway 1 and the Auckland Northern Motorway...
has been proposed. Investigation as part of the tunnel link project raised questions about safety of such an option, but it has not been ruled out. Some of the pillars for the second tunnel approaches are visible in the Clifton Terrace carpark adjacent to the cable car line, as is some of the approach road which currently forms part of the upper deck of the Clifton Terrace carpark. These pillars may also be seen on the left hand (eastern) side of the "Wellington Terrace Motorway, looking south" webcam on the CityLink website (http://citylink.co.nz/products/webcam/terrace-south/).
As you enter the tunnel it is impossible to see the other end, as it curves in the middle.
State Highway Status
When it opened in 1978, the tunnel was the southern end of State Highway 2. Alterations at the Ngauranga SH1/SH2 interchange in 1984 connected SH1 to the motorway; although SH1 continued off the Aotea Quay offramp until 1996. In 1996 Transit extended the SH1 status to the entire route from the end of the Wellington Urban Motorway to Wellington International AirportWellington International Airport
Wellington International Airport is an international airport located in the suburb of Rongotai in Wellington, the capital city of New Zealand. It is a secondary hub and focus city for Air New Zealand and its subsidiaries...
. From 2007 this is via the Wellington Inner City Bypass
Wellington Inner City Bypass
The Wellington Inner City Bypass is a westbound one-way road varying from two to four lanes largely at ground level in central Wellington, New Zealand, part of State Highway 1, and was opened in March 2007....
.
Systems and Safety Upgrade, 2011
In order to ensure that the tunnel continues to operate effectively the NZ Transport Agency (NZTA) is upgrading the fire fighting, lighting, ventilation and drainage systems, building new tunnel control buildings and making some earthquake safety improvements. This work will extend the working life of the Terrace Tunnel. Work is currently underway and is due for completion late 2011 or early 2012.Upgrade works are being completed by the Wellington Tunnels Alliance - formed by Leighton Contractors, SKM, Aecom and NZTA.
Future of Tunnel
The future of the corridor incorporating the tunnel is part of the wider Ngauranga to Airport Study being undertaken by the national state highways agency Transit New ZealandTransit New Zealand
Transit New Zealand was, from 1989 to 2008, the New Zealand Crown entity responsible for operating and planning the New Zealand State Highway network...
. The study indicates a cost of (NZ) $80 million for a second tunnel.
It has been proposed as of December 2009, that a second duplicate tunnel will be constructed within the next 10 years.