Wellington Urban Motorway

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The Wellington Urban Motorway, part of SH1, 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.

From the Ngauranga Interchange (State Highways 1 & 2), the motorway travels south across a narrow piece of land alongside the Wairarapa and North Island Main Trunk railway lines. After passing through the suburb of Kaiwharawhara, the motorway travels across the 1335m long Thorndon overbridges, the longest bridges in the North Island, before entering the suburb of Kelburn. Shortly after it enters the Terrace Tunnel before terminating at Ghuznee Street in Wellington City.

[edit] History

The Wellington Urban Motorway in 1994, looking north out of Wellington. The motorway shares a narrow stretch of land with the North Island Main Trunk Railway and the Wairarapa Line.

The concept for the Wellington Urban Motorway first arose from the De Leuw Cather report on Wellington urban transport in 1963 which proposed a "foothills motorway" to be built from Ngauranga to the Mt Victoria Tunnel. The alignment and scale of the motorway between Ngauranga and the Bowen Street overbridge as built very closely matches the original proposal, with the one exception that the proposed interchange at Ngaio Gorge (with on and off ramps over the railway to Kaiwharawhara) was never completed, although the stumps of a southbound on ramp and northbound on and off ramps remain visible today broadly parallel to Kaiwharawhara railway station. Beyond the Tinakori Road and Hawkestone Street on/off ramps going south, the motorway is a considerably scaled down concept from what was initially proposed.

The first phase of the motorway was opened between Ngauranga and Aotea Quay in 1969 as part of State Highway 2, relieving the chronically congested traffic signal controlled intersection at the base of the Ngauranga Gorge which endured peak time delays of several kilometres at AM and PM peaks. The motorway was extended in phases as far as Hawkestone Street/Tinakori Road by 1974. However it's last major extension was completed in 1978, with the construction of the Terrace Tunnel and the termination of the motorway at Ghuznee/Vivian Street.

The original concept was for 6 lanes to proceed to Willis Street, with the existing Terrace Tunnel being the northbound route, and a duplicate tunnel southbound. The current alignment of the motorway up to the Terrace offramp clearly shows how 6 lanes were quickly curtailed to three, by using the Terrace interchange to lose a lane each way, and a third lane merging southbound towards the remaining tunnel. The Shell Gully/Clifton Tce carpark under the motorway, accessible from the Terrace clearly shows the pillars, and part of the carriageway (now part of the carpark) that would have carried the additional three southbound lanes to the 2nd Terrace Tunnel.

Funding for the second tunnel was indefinitely shelved in the 1970s due to fiscal pressures on government, and the beginning of far greater scrutiny of the quality of highway expenditure. It was clear that until the Wellington Urban Motorway was connected to State Highway 1 at Ngauranga Gorge, that a single Terrace Tunnel would be adequate for the traffic demands of the 1970s.

The Ngauranga Interchange connecting State Highway 1 opened in 1984, removing the State Highway designation from the Hutt Road south of Ngauranga, and making the Wellington Urban Motorway between Ngauranga and Aotea Quay both State Highway 1 and 2. While the Ngauranga Interchange relieved the severe congestion experienced at the traffic light controlled intersection at Ngauranga, it did double the usage of the rest of the motorway, generating peak time congestion at the end of the motorway, and in the AM peaks with merging traffic from the Hutt.

Meanwhile, the original plans to extend the motorway beyond Willis Street had been significantly reviewed, with a new plan for an "arterial extension" at a 70km/h standard proposed along the motorway alignment towards the existing Mt Victoria Tunnel (the original full motorway plan had been scrapped, as it would've meant the destruction of the Basin Reserve, and an unaffordable duplicate Mt Victoria Tunnel). This plan in itself had been shelved because the congestion levels did not warrant it, and the beginning of localised community opposition to the project.

Until 2006 the northbound motorway started at the Vivian Street onramp. On 28 December 2006 this onramp was closed, with a new northbound onramp at Karo Drive as part of the Wellington Inner City Bypass.

Until 2007 the southbound motorway terminated at the Ghuznee Street offramp. On 25 March 2007 this offramp will be closed, and traffic diverted to a new Vivian Street offramp along the line of the former onramp.

The Motorway is the subject of the ongoing Ngauranga to Airport Strategic Study, which is investigating Wellington City's future transport growth needs.

[edit] See also

List of motorways and expressways in New Zealand