Auckland Harbour Bridge

The bridge from Watchman Island, west of it.

The Auckland Harbour Bridge is an eight-lane, box truss motorway bridge over the Waitemata Harbour, joining Saint Marys Bay in Auckland City with Northcote in North Shore City, New Zealand. It has a total length of 1,020 m (3,348 feet), with a main span of 243.8 m, rising 43.27 m above high water^[1] (even though few large ships pass under it). It is part of the Auckland Northern Motorway running from the Central Motorway Junction in downtown Auckland to Orewa.

Construction

Background

Prior to construction of the bridge, the quickest way of getting from Auckland to the North Shore was via one of the regular passenger or vehicular ferries. By road, the shortest route was through West Auckland via Riverhead and Albany, a distance of over 40 kilometres.

Initial structure

The bridge took four years to build and was opened on May 30, 1959 by Prime Minister Sidney Holland, with four lanes of traffic, two in each direction. Four men were killed during construction, and their names are recorded on a memorial plaque underneath the bridge at the Northcote end.

The bridge started out as a toll bridge, with toll booths for both north and south-bound traffic located at the northern end. Tolls were originally 2/6 (25 cents) per car but were reduced to 2/- (20 cents) after 15 months of operation. Later, tolling was made south-bound only before being finally discontinued on March 30, 1984, and the booths were removed. This was in line with political commitments that tolls would only be charged until the bridge's constuction costs were paid off.

'Nippon clip-ons'

Support structure under the bridge.

The bridge was originally built with four lanes for traffic. Owing to the rapid expansion of suburbs on the North Shore and increasing traffic levels it was necessary to increase the capacity of the bridge.

In 1969 two-lane box girder clip-on sections were added to each side, doubling the number of lanes from four to eight. The sections were manufactured by Japanese contractors (Ishikawajima-Harima Heavy Industries Co., Ltd.), which led to the nickname 'Nippon clip-ons'. They have an expected lifetime of 50 years.^{[citation needed]}

In 2006, it became public that cracks and signs of material fatigue had been found in the clip-on lanes. Auckland City Council Transport Committee requested Transit New Zealand to investigate the future of the clip-on lanes as part of its 10-year plan. Transit noted in this context that the plan already includes some funding for bridge maintenance.^[2]

In May 2007, Transit New Zealand proposed a bylaw change to restrict trucks over 4.5 tonnes from using the outside lane on each clip-on. This is to reduce stress on the aging structure.^[3] This was later changed to a less strict bylaw introduced in July 2007 restricting only vehicles of 13 tonnes or more, based on the high level of voluntary compliance during the previous months.^[4]

In 2007, it was announced that NZ$ 45 million in maintenance work on the clip-on sections was being pulled ahead as part of good practice. However, in October 2007, a 2006 report from Beca Group surfaced in the press, noting that the clip-ons were at risk of catastrophic, immediate failure in certain circumstances (such as a traffic jam trapping a large number of trucks on them). Transit New Zealand has noted that the situation described was extremely unlikely, and measures already implemented would prevent it from occuring.^[5]

Traffic management

A "tidal flow" system is in place where the traffic direction of two of the centre lanes is changed in order to provide an additional lane for peak period traffic. During the morning rush, five of the eight lanes are allocated to southbound traffic heading towards Auckland. This situation is reversed in the afternoon, when five lanes are allocated to northbound traffic. At all other times of the day the lanes are split evenly, and peaks also have grown increasingly evenly distributed (i.e. whereas in previous decades (as late as 1991), there was often a higher than 3:1 difference in directional traffic, this has now (2006) dropped to around 1.6:1). The bridge has an estimated vehicle capacity of 180,000 per day, and in 2006 had an average volume of 168,754 vehicles per day (up from 122,000 in 1991).^[6]

For many years lane directions were indicated by overhead signals. In the late 1980s a number of fatal head-on accidents occurred when vehicles crossed lane markings into the path of oncoming traffic. In 1990, a movable concrete safety barrier was put in place to separate traffic heading in opposite directions and eliminate head-on accidents. A specially designed barrier machine moves the barrier by one lane four times a day, at a speed of 6 km/h. It takes 40 minutes to move the entire barrier.

Second Harbour Crossing

Bridge from the Sky Tower, southeast of it.

Background

Even with the clip-on section and the traffic management in place, the Harbour Bridge is experiencing severe congestion during rush hours, which will only get worse as North Shore City grows and Auckland City becomes more densely settled. Therefore, there is growing pressure for another harbour crossing. Many have also noted that such reliance on a single asset (which might experience failure via an earthquake or other disaster) is not in the interests of either Auckland or New Zealand.^{[citation needed]}

However, a recent (2007) study by the Auckland Regional Council has shown that peak hour traffic volumes are actually down compared to early 1990s. The morning peak (from 7 am - 9 am) has dipped from 17,048 vehicles inbound (towards Auckland City) in 1991 to 16,032 vehicles in 2006 (though the opposing traffic did climb from 5,872 to 10,555 vehicles). At the same time, the afternoon peak (from 4 pm - 6 pm) has fallen from 17,092 vehicles outbound to 16,759 (though again, the opposing traffic rose substantially, from 6,944 to 10,991). This is generally attributed to travel demand management and to drivers avoiding peak hours, and has raised some doubts about whether a second crossing is actually necessary.^[6]

Several projects either side of the bridge are also currently (2007) underway or planned to ensure that the motorway capacity on both sides matches that of the peak time capacity of the bridge (a factor which is considered by some to be more of a bottleneck than the bridge capacity itself),^[6] and to enhance the attractiveness of public transport. These include the upgrade to the Central Motorway Junction, the Harbour Bridge to City Tunnel (Victoria Park Tunnel) (which will increase capacity between the Central Motorway Junction and the bridge by 50%)^{[citation needed]} and the Northern Busway (which will provide a bypass parallel to the Northern motorway as it approaches the bridge). The future timing of an additional harbour crossing may also be delayed by the completion of the Western Ring Road (a combination of upgraded and new motorway skirting the western edge of the harbour and suburbs), which will provide some relief for traffic travelling between the North Shore City and West Auckland. This route is expected to be completed by 2020 at the latest.^{[citation needed]}

At the moment, official political statements still conclude a second harbour crossing is to be delayed (though it should be noted that the District Plan is a document updated only once or twice every decade):

The [Auckland City] Council will work with Transit New Zealand, the ARC, and the North Shore City Council to develop and implement measures, designed to optimise the future use of the existing Harbour Bridge and its approaches, for the peak period movement of people. This is to avoid or substantially delay the need to construct a second crossing of the Waitemata Harbour.^[7]

However, the current (2007) discussions about future traffic plans in Auckland, as well as for the Western Reclamation (an area where a proposed crossing alignment was to be anchored) have put the plans for a second crossing back into public discussion, though most of the plans would still envisage the actual construction to be one or two decades away.

Proposed crossings

Possible alignments

Several solutions have been proposed, including building another bridge alongside the existing one, a tunnel, or combinations of both. Following a detailed scoping study undertaken in 1996, Transit New Zealand identified its preferred options for a new crossing - either a new bridge approximately 500 m west of the bridge connecting to the North-Western Motorway (SH16) via a tunnel underneath Ponsonby and Grey Lynn, or a tunnel slightly to the east of the bridge connecting to the Central Motorway Junction via twin cut-and-cover tunnels under the western CBD / Victoria Park.^[8]

In 2006, Transit New Zealand noted that its 10-year plan, at that time being consulted on, would include funding for another study into a second harbour crossing.^[2] This study has now been declared to include the possibility of landing a future tunnel underneath the Tank Farm, with a connecting tunnel to south of Victoria Park. Costs are estimated at NZ$ 3 billion.^[9] Some commentators like Brian Rudman have noted that it would make the most sense to keep the new crossing for public transport only, possibly to connect with a rail tunnel to Britomart Transport Centre.^[10] This statement was largely supported by North Shore City mayor George Wood, who noted that public transport provision on the new crossing (including the possibility for light rail or heavy rail to connect to Britomart) had been part of North Shore City Council's plans for many years.^[11]

A possible tunnel between Mechanics Bay and Northcote may also be considered in the feasibility studies, but is appearing unlikely due to criticism from local groups, as well as due to the denser residential zones and geographic difficulties faced on such an alignment.^[12]

Replacement bridge

During the public discussions in 2007, an interest group also put forward a proposal to build a new, much larger bridge to the east of the existing structure, and demolish the old Harbour Bridge. They argue that the new bridge, which would be about 50% longer than the existing one, could be constructed to provide for dedicated public transport (including light rail, which is credited with allowing a tripling of the total capacity in people moved over the existing Harbour Bridge), as well as for cyclists and pedestrians. Significantly, they argue that the new bridge would more or less pay for itself, by freeing up new residential land (currently taken up by several km of motorway approaches) in some of the most sought-after Auckland locations like Saint Marys Bay. The proponents claim that the bridge would put more than 35 hectares and open up 3.3 km of shoreline, a prize which would more than make up for the fact that the plans for the Western Reclamation redevelopment would in this case find themselves partly compromised by a major motorway in its area. The new bridge would also be cheaper to operate and would not need emission vents like a tunnel.^[13][14]

The new bridge design, a cantilever spar cable-stayed bridge, was proposed by the Jasmax architectural firm, which note the 'Anzac Centenary Bridge' would be buildable in time for the 100-year memorial of the Gallipoli landings in 1915.^[13]

See also

General

• Public transport in Auckland
• Transport in Auckland

Specific

• Central Motorway Junction, the major motorway junction connecting southeast of the bridge
• Newmarket Viaduct, similarly important traffic bottleneck on other side of Auckland CBD
• Western Reclamation, large industrial area east of the bridge, possible site of 2nd crossing

References

Before bridge construction, looking south over Northcote Point towards Auckland City in 1947.

1. ^ 1951-1961 The Auckland Harbour Bridge Authority (Auckland Harbour Board publication, 1960s)
2. ^ ^{a b} Harbour Bridge future questioned - Television New Zealand, Sunday 12 March 2006
3. ^ Trucks to be banned from clip-ons - Television New Zealand, Friday 4 May 2007
4. ^ Transit bans large trucks from clip-ons to extend life of lanes - New Zealand Herald, Tuesday 17 July 2007
5. ^ 'Catastrophic failure' warning on Harbour Bridge - New Zealand Herald, Sunday 14 October 2007
6. ^ ^{a b c}
7. ^ Auckland City District Plan - Isthmus Section, Chapter 12.6.2.4
8. ^ Feasibility study - Watemata Harbour Second Crossing (from the Transit New Zealand website)
9. ^ Tank Farm route for $3b tunnel (+map) - New Zealand Herald, Tuesday 10 July 2007
10. ^ Brian Rudman: Hallelujah, talk before bulldozers - New Zealand Herald, Wednesday 11 July 2007
11. ^ Letters to the editor - Harbour tunnel - Wood, George; New Zealand Herald, Saturday 14 July 2007, Page A22
12. ^ Bayswater tunnel could be part of harbour crossing study - New Zealand Herald, Monday 09 July 2007
13. ^ ^{a b}
14. ^ Photo: Longer, more elegant harbour bridge dreamed up - New Zealand Herald, Tuesday 08 May 2007

External links

• Auckland Harbour Bridge in the Structurae database
• Historical photos (from the Transit New Zealand website)
• Historical photos (from a private website)

• Maps and aerial photos Coordinates: -36.830722° 174.748793°
  • WikiSatellite view at WikiMapia
  • Street map from Google Maps or Multimap.
  • Satellite image from Google Maps

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