Local Government Magazine
Assets & Asset Management

Tasman District Council – Modelling assets

Outcomes from modelling an asset network effectively can help justify funding in a council’s next Long-Term Plan. Tasman District Council has been doing just that. Here are some insights into how its roading asset deterioration modelling has worked so far.

Councils are updating their Activity Management Plans (AMPs) and Long-Term Plans (LTPs), in conjunction with preparing business cases for 2018-2021 investment through the National Land Transport Fund. This means roading asset managers again face the challenge of ensuring they have a solid and reliable evidence-based business case to secure their funding.

Tasman District Council owes part of its success to investing wisely through asset deterioration modelling to help secure funding. The network has been hailed as an example of industry best practice.

Transportation manager, Jamie McPherson, manages 1750 kilometres of roads including 90 kilometres of sealed roads in the Tasman region. He is responsible for the outcomes of the council’s roading network condition and performance, and making sure his community is getting value for money. Historically, the district’s large roading network has had a good level of investment and, overall, is in good condition.

Big on primary production, the three big ‘Fs’ of forestry, fishing and farming are the mainstay of the region’s economy. In recent years, the district has experienced rapid growth including Aucklanders shifting to the region in search of a better lifestyle, and a growing expat community. This has put pressure on infrastructure budgets, especially with an ageing population and relatively low incomes.

Jamie says the local community is struggling with the same challenges that other communities face: “as we grow, expectations increase in terms of outcomes”.

Over the past four years, the council has reduced its roading resurfacing and rehabilitation budgets by 30 percent compared with historic budgets and was beginning to become concerned about the longer-term consequences of lower budgets.

“There was a push within our council to save costs and reduce debt projections,” says Jamie. “So, we needed to carry out modelling on our roading network to ensure that a reduction was feasible.”

He wanted to test different investment scenarios to know if council was spending the right amount of money.

“It’s the million-dollar question for any council, and modelling has been part of the way for us to answer that question. We can plug in different scenarios. What if, for example, we only spent $2 million annually? Or what if we increased that to $3 million in future years? We can play around with those options and it tells us what the outcome might be or the consequences of those decisions.”

Jamie adds that any evidence to justify investment needs to be believable and as accurate as possible.

“It has to tell a story and be understandable, and sometimes that’s a challenge. It’s very easy for a technical person to produce a technical report that other technical consultants can read, but it’s much harder to translate that technical information into easily-digestible summaries on which senior councillors and management can make strategic decisions.”

Jamie and his team have used the IDS modelling tool (built within the dTIMS Software) via contractors over the years which has helped their roading network get to the standard it is today. The most recent run was done directly with IDS late last year.

“I directed them on what outcomes we were looking for; which was to understand the long-term effects of decisions we make today about resurfacing and rehabilitation budgets in our AMP and LTP,” says Jamie. “I supplied access to our Road Assessment and Maintenance Management (RAMM) database and specified the investment scenarios that we wanted modelled which included low, normal, high and a combination of low-normal.”

Data plays an important role in modelling any asset network; the accuracy of the outcomes and recommendations improve as the amount of good data increases. However, most local authorities have limited detailed condition data and Tasman District is no different.

“We have high speed data for about 30 percent of our network, and some falling weight deflectometer strength information,” says Jamie. “But there is always the uncertainty about how confident we can be with the results – an issue that most local authorities have to deal with.”

Region covered by Tasman District Council showing the ward boundaries.

Jamie advises that the more that is known about a pavement, the more possible it is to tailor the rate of deterioration. “If you have better data, the better you understand how the pavement will actually deteriorate and the outcomes and results from the analysis are more accurate. Recommendations from IDS through the analysis help me take that information within my organisation and justify future investment in data collection and improvement.”

Outcomes and the future

Sharing some of the outcomes of Tasman District Council’s recent modelling project, Jamie says, “We received answers to how different investment levels would affect the long-term condition of our sealed network, in terms of roughness, cracking and surface age. We’ll also use the results as an initial input into updating our forward works programme.”

One outcome he wasn’t expecting was that all scenarios suggested council would need to increase the amount of resurfacing on its rural access roads. “I was not anticipating this as the ONRC had us in the mindset that higher class roads should get more and everything else will get less.”

The quality of the analysis reporting has also improved over the years, says Jamie. “In this latest modelling report, IDS is helping our consultants to write information in a way that is more understandable. For example, in the executive summary, easy FAQs such as ‘What does all this mean?’ and ‘Is the current resurfacing rate adequate?’ provide answers to those simple questions which is really handy. The report still has the technical geeky stuff in the back that people like me can read.”

Looking to the future, Tasman District Council faces an increase in truck weight limits and the potential impact on local roads and, in particular, weaker pavements, especially considering the forestry and farming focus in the area. Jamie says data collection is key.

“For some of our roads, we need better strength data because we don’t know how strong they are underneath. We need to collect high-speed data to track if the roads are getting worse over time. Like everyone else, we have been grappling with investing enough to protect the condition of our assets against these bigger, heavier trucks.”

He continues, “The outcomes from the modelling this time around gave us enough confidence that, overall, our condition is not going to worsen a lot. But, again, we need to test some of the assumptions and the only way to do that is by collecting better data. IDS’s experience and overview of dTIMS across a range of other networks provided some recommendations on what further data we should collect. That will help us justify prioritising expenditure on data collection.”

Jamie concludes, “Overall, this latest modelling project helped us develop confidence and commit to a ‘low-normal’ investment scenario, with lower spend on resurfacing and rehabilitation for another three years before returning to what we consider ‘normal’ investment in historical terms.

“This means we can save our community money in the next few years without compromising the future condition of the network. Our next steps are to field validate the modelling outputs as part of updating our forward works programme and we plan to develop a data collection strategy.”


This article was first published in the July 2018 issue of NZ Local Government Magazine.

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