Carriageways

Hamilton City has a complex, predominantly urban road network

The total road length in the city is 751 km with a good proportion of the network made up of relatively low traffic residential streets.

Figure 41. shows the breakdown of the HCC carriageway network by One Network Road classification (ONRC)

The carriageway network is surfaced with almost exclusively (98%) bitumen based products. More than half of the roads in Hamilton have a low cost chipseal surface. A summary of surface types that make up the carriageway network is shown in the table below. 

The distribution of carriageway surface age is shown in the chart below. Almost 32% of the network has a surface older than 15 years. 

Roughly, the same proportion (not necessarily the same sections) has a pavement older than 50 years. This is around the expected useful life for base course layers. Most older pavements that have exceeded their useful life are on higher classification roads.

The Hamilton road network in recent years has experienced consistent growth. This trend is predicted to increase over the next LTP period. We have optimised the level of investment for carriageway assets taking into consideration our maintenance strategies to maximise asset life through the application of timely preventative maintenance treatments and alternatives to costly traditional rehabilitation treatments.

The strategic link for carriageway maintenance is shown in the following table. 

The strategic link for carriageway renewals is shown in the following table. 

Hamilton city has seen consistent population and road network growth over the last 10-years as evidenced by the chart below. The growth trajectory evidenced since 2010 is predicted to continue into the foreseeable future.

This trend may even accelerate over the next ten years as residential development continues to increase with the potential to add up to 1400 residences per year. If all these homes were to occur as green field development, it is possible that the road network could increase between 10 to 12 kms per year. With some brown field development It is likely that the increase will be in the order of 12 to 14 kms per year.

This does not take into consideration revocation of State Highway carriageway sections, new road construction or boundary changes. 

Although not 100% confirmed, it is expected that the completion of the Waikato Expressway will add an additional 25 kms of current State highway to the HCC road network.

The forecast growth of Hamilton proposes challenges to the efficient delivery of the carriageway activity. 

Hamilton City utilises a range of network classifications to determine asset criticality. These are defined below.

The One Network Road Classification (ONRC) is a definition of asset criticality which takes into account the traffic volumes and composition, connectivity and linking, freight and tourism usage, and hospital access. 

Hamilton’s Network Operating Framework brings in a further level of detail taking into account active modes such as walking, cycling and passenger transport. 

The road network is highly resilient and should an incident or event cause the closure of any road, alternative routes and detours can typically be set in place.

Sites have been identified sites that are critical to the running of the city to ensure that reasonable steps can be taken to manage the risk of loss of access due to external events, and to ensure that plans are developed to reinstate access as rapidly as possible (refer to Part 7). HCC critical sites are the:

• Waikato Hospital which has its main access off Pembroke St;
• Water treatment plant accessed off Peacockes Road;
• Waste Water Treatment plant accessed off Pukete Road;
• Chorus Central Telephone Exchange accessed off Anglesea St;
• Fire stations on Vickery Street, Anglesea St and Crosby Rd;
• Ambulance stations on Hukanui Rd and Seddon Rd; and
• Waikato River bridges and approaches

The collection of network condition data is extremely important in order to facilitate robust decision making. The data collected should be optimised to maximise its usefulness to decision making.

Complete and relevant condition data is required for;

• Developing robust Forward Work Programmes (FWP), both for near and long term planning
• Enabling decision making regarding maintenance vs. renewal
• Highlighting potential safety issues such as low grip or damaged structures
• Preparing regulatory network performance reports by the Transport Agency

Condition rating surveys of all sealed roads carrying more than 2,000 vehicles per day are undertaken annually. Roughness and condition rating surveys of all sealed roads are undertaken at least every second year. 

Roughness is a measure of unevenness within the carriageway.  Rougher roads have a negative impact on safety and vehicle operating costs and customer perception. This is one of the factors used in forward work or maintenance programming. However, the primary value of NAASRA is as a network-wide indication of the level of service. Roughness is the primary parameter in reporting the Smooth Travel Exposure metric.

Below is a dashboard showing an overview of Network Performance for Hamilton City Council

High Speed Data Surveys

HCC has adopted the data collection strategy developed by the RATA (Regional Asset Technical Accord) group and is currently undertaking high speed data surveys of the carriageway network. These surveys measure and record both surface and pavement defects such as rutting, roughness and cracking. 

RAMM Condition Rating

The RAMM rating survey results are important for calculating the Pavement Integrity and Surface Condition Indices. This survey involves a visual inspection of a 10% sample of each carriageway treatment length. Faults within that sample are classified, measured and recorded. This work is currently being carried out externally for City Transportation by consultants.  

All Faults Inspections

The Infrastructure Alliance uses the All Faults visual condition assessment process to record and manage carriageway defects. Carriageway (including footpath and drainage) defects are recorded and categorised by type, dimensions and assigned a severity rating. If appropriate, a treatment and timing for treatment is also recommended. The entire network is inspected at least once a year. This allows for a review of old faults and the addition of new ones to the database. All faults defect data is collected on a geographic sector basis, with the frequency prioritised by ONRC classification.

Carriageway data confidence is summarised in the following table. Overall, we are confident that carriageway data is reliable. Data grading is based on 

The ONRC uses roughness as a measure to define customer and technical levels of service for the carriageway activity. Managing roughness provides a customer focussed way to maintain carriageway condition and is the predominant measure of service from a ride comfort perspective. 

Performance against the ONRC customer measures is detailed in the following section of this document.

We have calculated roughness condition bands, using the ONRC metrics for peak and average roughness as a basis, to describe the carriageway in range of condition dates from Very Good to Very Poor as shown in the chart below.

Urban carriageway sections show higher roughness than the rural sections. Secondary Collector and Access roads have the highest proportion of poor and very poor roughness on the network.

Assessing current performance against the levels of service for provides evidence that the management practices in place at HCC are delivering the agreed level of service the carriageway asset. Gaps in the achievement of the levels of service identify areas for improvement. The following pages identify the current performance of the carriageway against the ONRC customer and technical levels of service, and are summarised in the table below.

Safety Customer Outcome 1

Safety Customer Outcome 2

Safety Customer Outcome 3

Safety Technical Outcome 4

Safety Technical Outcome 6

Amenity Customer Outcome 1

Amenity Customer Outcome 2

We have developed options for the Carriageway asset based on increasing and decreasing the current renewal budget as follows: 

We use the Deighton Total Infrastructure Management System (dTIMS) to assess the efficacy of these options by applying two models with different optimisation routines as described below.

The IDS dTIMS model was used to model the condition outcomes for five budget scenarios and consider the outcomes in terms of customer level of service outcomes and technical outputs.

The impact of investment on customer levels of service is not dramatic as shown below on the average roughness prediction by budget scenario. Rehabilitation treatments have the largest impact on average roughness improvement. Therefore, the customer levels of service indicators are not deemed particularly sensitive to rehabilitation levels.

For comparative purposes, the chart below provides the long-term return in surface condition, relating to the look of the network (e.g. potholes, cracking, chip loss etc.). This comparison clearly shows that the surface condition will drastically deteriorate should the renewal budget be reduced. Resurfacing treatments have the largest impact on surface condition. Therefore, the network is more sensitive to changes to investment in resurfacing.

We have assessed our options against the GPS, ONCR outcomes and the HCC problems statements as detailed in the table below.

Option 3 provides the best positive impact on the strategic outcomes of all the options considered.

While network surface condition is maintained through the resurfacing programme, the optimal model predicts an ever increasing pavement age across the Hamilton city network. Targeted investment will be applied to maintain and/or minimise

All Faults inspection data is the primary source of information for short term maintenance. The maintenance programme is developed using a combination of the All Faults data and the associated Target Cost Estimate for the repair type. A monthly programme is developed using the prioritisation methodology based on ONRC road classification and described in the figure below. This ensures tasks are completed in order of importance whilst being cognisant of:

• Network Trends
• Maintenance strategies
• Task prioritisation
• Risks with alternative maintenance standards
• Summary of future costs
• Clustering efficiency

The strategic link for carriageway maintenance is shown in the following table. 

Carriageway renewal is a major work activity which restores, replaces or rehabilitates an existing asset to its original capacity. There are two types of renewal carried out on the carriageway asset; resurfacing and rehabilitation:

• Resurfacing by replacement of either chipseal or asphalt (asphaltic concrete);
• Rehabilitation by granular pavement replacement or by structural asphalt (asphaltic concrete) layer construction.

Creating a renewals programme is a complex undertaking, requiring the successful completion of many processes to ensure a robust forward works programme of renewals is developed, these include:

• Data collection and preparation
• Data analysis and scenario modelling
• Field validation and model alignment
• Economic justification (NPV)
• Outcome verification
• Final programme formulation

We use a set of strategy envelopes to help inform our treatment selection process, as shown in Figure 54

This helps create a first cut of possible treatment options based on the current and predicted condition of the carriageway section. The parameters to identify candidate sites for future treatment are also used in our predictive modelling tools.

The strategic link for carriageway renewals is shown in the following table. 

Hamilton has a significant proportion of roads with asphalt surfacing and low traffic volumes, typically built as part of residential subdivisions, the oldest of which are reaching the end of their expected useful lives. We have a strategy in place to manage the renewal of these surfaces to balance least life cycle cost and risk considerations.

Chip seal is a significantly cheaper treatment and can perform as well as asphalt in specific circumstances. Our strategy states that asphalt surfacing will only be considered in the following situations:

• Where traffic volume exceeds 15,000 vehicles per day;
• Areas of high turning stresses (e.g. busy intersections or cul de sac heads);
• Roads in industrial or commercial areas where there is a high concentration of heavy commercial vehicle traffic;
• Roads with short sections between two adjacent asphalt areas;
• Roads subject to high pedestrians use, e.g. the CBD;
• Roads requiring special treatment for engineering reasons
• Compliance with Resource Consent requirements, e.g. low noise surfacing; and
• Where the whole of life cost can be proven to be less than alternatives.

The analysis which formed the basis for this strategy considered the life cycle cost and risk associated with treatment options as indicated in the table below. Option two was chosen as the best balance between cost and risk and is being monitored to ensure it is providing a value for money solution.

Treatment selection for pavement rehabilitation basically comes down to two options:

• Granular pavement overlay or replacement
• Structural Asphalt Inlay

Structural Asphalt has typically been viewed as a more expensive option when only the direct cost is considered, but it does provide any benefits which when taken into account provide a better result for the network and customers:

• Minimises the depth of material removal required when construction is constrained e.g. by kerb and channel height;
• Minimises the possibility of conflict with services under the road surface;
• Construction can be carried out in a much shorter timeframe causing less disruption to the network; and
• Work can often be undertaken during off peak hours to minimise disruption.-

Advanced Pre-Reseal Repair Treatments

Delivery of pre reseal preparatory repairs the year prior to resurfacing treatments is considered best practice in pavement operations. We have made allowance to move to this practice over time, bringing forward a portion of the next year’s preparatory repairs each year for the first three years of the LTP. This should allow us to deliver this work type within current resources, whilst moving to more advanced delivery of our carriageway renewals.

Renewal Decision Making Process

Potential candidates for renewal treatments are identified using All Faults data, dTIMS renewal forecasts, and engineering judgement. These sites are investigated in detail as part of our forward works development process. For the data analysis and scenario modelling we compare and contrast evidence we have at our disposal from multiple predictive models as described in the table below. We utilise our All Faults data along with the High Speed Survey data as inputs to our predictive modelling.  

These models give us different perspectives on the future need for the carriageway asset in terms of renewals. Field validation and model alignment occurs once we have refined the model outputs in the office. A virtual drive over of treatment sites eliminates sites where there are obvious benefits to delaying treatment, such as aligning with capital works or development programmes.

We use the JunoViewer and Juno FIT field validation tool to manage the forward works programme, taking FWP information into the field on handheld devices and capturing field notes and photographs to aid in the decision making process, as described below

Rehabilitation sites are analysed in detail to determine if they can be justified according to the criteria in the Transport Agency’s Economic Evaluation Manual. Sites are justified when the whole of life cost is lower for the renewal option than the do nothing or do minimum options.

Funding Request

Core Programme

Our analysis shows that Option 3 gives the lowest total expenditure over a 10-year period without significant increase in maintenance cost, and level of service risk. This programme has been sought in the funding request.

Enhanced Programme

Option 5 which increases renewal investment and reduces maintenance cost would increase total cost, with a small reduction in maintenance cost and marginal improvement to the level of service. The benefits of this option do not outweigh the costs and funding for this option has not been sought.

Renewals versus Depreciation

The chart below shows that recent years and forecast renewal investment remain less than current (and historic) annual depreciation values. The level of funding requested for the next LTP period equates to 94% of the annual depreciation in 2021.

Consequences

The risks and implications of not funding the renewal activity for the carriageway assets have been summarised in the table below; aligned to GPS priorities and ONRC customer level of service outcomes.

Improvement Actions

HCC is in the process of putting together its Skid Resistance Strategy which will document how and where on the network skid resistance will be measured. This will allow us to identify sites with skid resistance issues and assign appropriate and timely treatment.

New pavements are built to meet the needs of growth and LOS. In addition to the need to build “new roads”, growth can drive the widening of existing pavements. Growth can also require the strengthening of pavements, as in the case of road pavements subject to increased heavy vehicle loadings.

The Local Government Act 2002 requires HCC to identify the projects it is carrying out to meet the demands of growth. The growth and demand section of this AMP includes this work in its recommendations for improvement.

Distinguishing between growth-driven and LOS driven improvements is difficult.  Additional traffic resulting from growth can result in LOS below agreed levels.  The work to restore the level of service to previous or currently agreed levels is treated as growth related.  It is easier to make the distinction when a LOS is deliberately changed, such as through the provision of cycle ways, the introduction of smoother surfaces or safety improvements.

Developers pay the full cost of local road development within new subdivisions, with new assets being vested to HCC upon completion and the grant of subdivision titles.  HCC specifies minimum design criteria (Infrastructure Technical Specification) and checks construction at critical stages.

Where a development fronts an existing legal road, improvements will often need to be made to that road, and sometimes to other parts of the network; for example, new seal, footpaths, kerb and channel, access improvements, increased seal width, and improved sight lines.   For each development’s resource consent process, HCC considers the need for consequential road improvements directly associated with the development.  This applies whether the proposal is for residential, industrial, commercial, or rural use. Where improvements are justified, engineering staff seek to have appropriate conditions inserted into consents and an agreement is made on cost sharing.  

For the proposed capital programme for pavements and more information on its development and prioritisation, see Part 6 of this AMP.

Disposal of carriageway assets is not a common occurrence on a growing road network but assets may become surplus to requirements for any of the following reasons:

• Under-utilisation;
• Obsolescence;
• Land has a more valuable alternative use;
• Assets are replaced before their predicted economic life expires;
• Upgrading or operating is uneconomic;
• Policy changes; or
• Service is provided by other means (e.g. private sector involvement).

The following information summarises our investment request to achieve the levels of service identified for the carriageway maintenance and renewal activity.