Where are we now? Dunedin's transport infrastructure

1.8 Where are we now? Dunedin's transport infrastructure

Resilience in the transport network infrastructure is under increasing pressure as many assets are becoming more at risk from flooding, erosion and king tides. Generally, the network has sufficient capacity with congestion only experienced in short morning and afternoon commuter peaks.

In the main urban areas, a small number of key intersections have safety or capacity issues. Mosgiel has capacity and safety issues at the Gordon Road/Gladstone Road intersection, including the rail crossing and the intersection of Quarry Road and SH1, which can cause traffic to back up onto the southern motorway at peak times.

Portobello Road along the Otago Peninsula and State Highway 88 to Port Chalmers have good provision for cycling and walking between suburbs and into the city centre. In the case of Portobello Road, the road does not allow for safe access to the shared path or public transport on the harbour side of the road (in some areas). In some places, the width of the road makes it either very costly or impossible to provide safe crossing points to the harbour shared pathway or locate bus stops appropriately.

The intersection between North Road and Opoho Road has safety, capacity and resilience issues, and the intersection between Great King Street and State Highway 1 remains a safety concern. The bottleneck at the North Road and Opoho Road intersection remains a challenge as it is physically constrained.

Other parts of the network experience congestion for short periods at peak times, but traffic volumes ease quickly, and this is not considered a constraint on future urban development.

Heavy vehicle movements continue to put pressure on road pavements and deterioration of roading assets is being observed. This is particularly evident on roads from the south to the Port and the inner harbour.

Over the past few years investment in renewals has not kept pace with depreciation and if not addressed will begin to impact levels of service, growth opportunities and future economic development.

The detail below presents the deferral of renewals in the past.

Kerb and Channel (network percentage completed)

• 2021/2022 0.8% completed vs target of 1.25%
• 2022/2023 0.7% completed vs target of 1.25%
• 2023/2024 0.7% completed vs target of 1.25%

Resealing (network percentage completed)

• 2021/2022 4.4% completed vs target of 6%
• 2022/2023 6% completed vs target of 6%
• 2023/2024 5.1% completed vs target of 6%

Footpaths (network percentage completed)

• 2021/2022 2.8% completed vs target of 4%
• 2022/2023 3.4% completed vs target of 4%
• 2023/2024 3.3% completed vs target of 4%

Dunedin's transport network is made up of $2.4 billion worth of assets (2024 replacement value). 50% of Dunedin's sealed pavements are aged 60 years or over (theoretical asset life ranges from 60 to 100 years).

Road surfaces in Dunedin have an age range of 9-25 years, and 6% of these surfaces are aged 20 years. 42% of these surfaces reach the end of their asset lifespan in years 10-20. The graphs below illustrate the age profile of various assets across the transport portfolio. These graphs indicate the complexity when planning from a budget perspective for asset renewal and illustrate how budget profiles for asset renewals are very rarely (if ever) linear.

Figure 7: Age profile of sealed pavements

Figure 7: Age profile of sealed road surfaces

Dunedin's roads have been built up over many years overlaying surfaces with a new seal. This has resulted in the crown of the road being higher than the kerb height in areas and reducing the capacity of the road to hold water during heavy rain events, as well as introducing issues for mobility users. The maximum number of seals should be six layers and 6% of the network currently has six or more seal layers with 16.9% facing a last seal (illustrated below).

Figure 8: Number of seal layers

Stormwater assets (kerb and channel, culverts and catch pits) represent 18% of the total value of the asset portfolio. The expected age for kerb and channel is between 60 and 100 years and approximately 31% of the assets are over 60 years (note labelled surface water channels in graph below). Kerb and channel condition ratings show signs of decline with 12% of the network in poor to very poor condition.

Figure 9: Age profile of water channels and kerb & channels

Figure 9: Condition of water channels and kerb & channels

Catch pits (mudtanks) have an expected life of 80 years. 72.6% of total catchpits are over 70 years old. Asset management of catchpits is normally through inspection, and they are graded according to their serviceability. Adequately maintained catchpits would be expected to live well beyond their expected (asset) life.

Figure 10: Age profile of catch pits

The asset life of a culvert is 80 years. 43% of these assets are over 70 years. Culverts are regularly inspected for condition and only a small number of culverts are rated in a poor condition. Culverts, however, are subject to influences outside of the asset more than most. Changes in weather patterns and surrounding vegetation can impact culvert performance significantly.

Figure 11: Age profile of culverts

Dunedin has 249 bridges, 728m2 of retaining walls and 101,969m2 of sea walls. Many of Dunedin's bridges are made of stone, wrought iron and steel with some early examples of reinforced concrete. Many other parts of New Zealand have a large component of timber bridges (which have shorter lifespans). In Dunedin, if bridges are suitably maintained there is no requirement for any major bridge replacements in the next ten years.

Figure 12: Age profile of bridge structures

Most of Dunedin's sea walls are made of stacked rock or stone. They have no estimated replacement date and are expected to last if they are fit for purpose (maintenance of these walls involves restacking the stone when required). The St Clair sea wall has design deficiencies so is regularly monitored and maintained and is currently structurally sound.

Most of Dunedin's retaining walls are masonry walls or concrete slope facings rather than structural retaining walls. A theoretical life of a retaining wall is 80 years,79% of current retaining walls are past their asset life.

Figure 13: Age profile of retaining walls

Dunedin's 989kms of footpath are predominantly made of asphalt (85%), the remaining are concrete, metal and slurry. Asphalt has a life expediency of 25-30 years; slurry has 10 years and concrete has 60 years. 23% of the asphalt footpaths are near the end of their asset life. In terms of condition, a reasonably high proportion of footpaths are in poor to very poor condition. In the past three years, footpaths rated poor or very poor represented 18% of the total footpath asset.

Figure 14: Age profile of footpaths

Figure 14: Condition profile of footpaths

The Smooth Travel Exposure survey (below) illustrates that the roughness of Dunedin's roads is increasing. In comparison to other local authorities, Dunedin performs poorly. Smooth Travel Exposure for urban roads has sat below the target measure for the past 11 years (a Department of Internal Affairs measure).

Figure 15: Percentage of travel on roads smoother than threshold

The graph below outlines renewal spend vs actual spend vs depreciation (in the past). Depreciation acts as an indicator for asset consumption, and it shows consistent and material under-investment in the past.

Figure 16: Depreciation vs renewals

Renewal quantities for the past six years are presented in the graphs below for reseals, footpaths and kerb and channel and show they have consistently been below asset management targets. This has led to a corresponding decline in asset condition and levels of service, and an increase in deferred renewals.

The 2024 Asset Management Plan and this Infrastructure Strategy propose sustained renewal investment. In 2024-27 this represents a 52% cost increase on the NZTA approved programme for 2021-24 and a 29% cost increase on the DCC’s 2021-24 forecasted spend.

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