The City of Onkaparinga in South Australia has engaged a new system to collect and model data on road conditions, giving the LGA more certainty when planning and prioritising maintenance work.

By Frances Sacco

Murray Conahan now knows more about his city’s roads than ever. As an asset planner for the City of Onkaparinga in South Australia, he has overseen a new system of condition rating for the city’s road network.

While every local government authority is required to collect data on its road network for accounting purposes every three to five years, Onkaparinga has gone a step further.

“Usually the type of data collected is fairly thin,” Conahan says. “It would have given us a rough overall guide to the state of the network.”

The new system gives planners at Onkaparinga a much clearer picture of the city’s road network and helps identify and prioritise work that needs to be done.

Two years on from the initial collection of that data, the city is now in the position to put it to work, pinpointing where repairs and reseals are needed most while calculating the materials needed to do the job.

Having this detailed information at a council officer’s fingertips has had the further benefit of making it easier to deal with residents’ complaints.

“It’s great to be able to say we have a transparent process in place,” Conahan says.

“They understand that we don’t just do Mrs Jones’ road because she shouts the loudest.

“And because I have the information in electronic form I can provide that information to residents in a more timely manner.”

Contractors collected the initial data over about two months in 2010.

The most complicated and time-consuming part of the process has been the data modelling, which is based on key trigger points, defect ratings and other factors such as soil types, road hierarchy and industry. 

“It took a bit of time playing around with the trigger points to get the system right,” Conahan says.

Downer EDI produced the modelling in conjunction with subcontractors IMG and AXIM. The initial results they produced had an accuracy rate of about 75 per cent. John Benge, Downer EDI’s South Australian Maintenance Manager, says those results were encouraging.

“It takes a bit of time to translate exactly how the engineers rate the condition of their roads into data that can be modelled, so the results were pretty good for the first time,” he says. Conahan agrees, saying the accuracy will improve over time.

“While we run this data to inform the works program, we still do a confirmation out in the field,” he says.

“We can use the data to run calculations to give us quantities of repairs and estimate how much needs to be done prior to refill.”

That data can also help decide what type of reseal or repair is needed. For example, significant kerb misalignment highlighted in an area with reactive soils may trigger use of an asphalt overlay, rather than a spray seal.

If significant pavement defects or cracking show up in the data, it could trigger a reconstruction project instead.

With the time taken to iron out data modelling problems, it will probably be about four years between the initial collection of data and the next round.

For the next few cycles, Conahan expects to collect the data every three years then, once they have established a baseline, the time frame could be pushed out to five years.

“The only pitfall is data integrity,” he says. “If there is an error in the data and someone spots it, then they wonder how they can trust the rest of it.

“But I don’t think I’ve ever seen a data set without at least one error, so you have to aim for a percentage and I think 75 per cent is pretty good first time around.”

Snapshot of Onkaparinga

The City of Onkaparinga was formed on the 1 July 1997 from the amalgamation of the Valley and Noarlunga with part of the District Council of Willunga.

Located on the southern fringe of Adelaide, South Australia and named after Onkaparinga River.

The largest LGA in South Australia, Onkaparinga has an estimated population of 164,800 and is expected to grow by 40,000 over the next 20 years.

It encompasses an area of 518 square kilometres and includes urban and rural communities.

The council is headquartered in the Noarlunga Centre with area offices situated in Aberfoyle Park and Willunga.

The City of Onkaparinga had the equivalent of 613 full time workers as of June 30 2011, including 33 externally funded positions.

The 2011-12 Budget incorporated $137.3 million of expenditure including $41.2 million on Major Projects, Projects and Capital Works and the Climate Change Response Fund.

Five ways Onkaparinga can use the data

1. To help officers explain road repair and resealing priorities to the community
2. To enable the planning, prioritisation and costing of maintenance and capital works.
3. To inform planners and workers of the types of treatment and material that are needed to fix a particular section of road.
4. To enable asset managers to provide a factual business case to their Finance Department to support funding claims and equipment purchases.
5. To enable asset managers to move toward a sustainable asset management approach to the management of their road network.

Five things to consider

1. Build a business case for the future management of your network. The additional money needed for more comprehensive data is well worth it, considering its value in capital and maintenance works planning.
2. Tailor the type of data collected to your region.
3. Have a comprehensive set of data collection guidelines to ensure data collection is consistent across the network.
4. Ensure adequate time is allowed to audit the data and refine the data model.
5. Update asset data whenever repairs are undertaken.

Comment below to Continue the Conversation!