The level of service we provide on our unsealed roads

Timaru District, like many Districts across New Zealand, has a large length of unsealed roads.

In general, our unsealed roads are managed affordably, with a fit-for-purpose level of service that the community can afford.  In comparison with our other rural provincial counterparts, our unsealed network performs well. Depending on traffic use, sections of certain roads will require metalling (shingle/gravel), which is considered from a network-wide view. Generally, grading is enough to keep most low-traffic roads in a suitable condition. Council staff regularly inspect and monitor unsealed roads, including using roughness technology measurement systems to check condition and plan future maintenance works.  The level of service on an unsealed road is lower than a sealed road, so slower speeds on these roads are generally required. When a road falls below the agreed level of service, unsealed pavement renewals are programmed. These generally happen from Autumn through to Spring when there is more moisture around.

Unfortunately, it is unaffordable for all roads in our network to be sealed. The short-term upgrade cost, as well as the ongoing maintenance cost for a sealed road, is significantly higher than an unsealed road.  These extra costs would need to be met by the ratepayer, and it is unlikely that this would be a financially prudent use of ratepayer funds.

Maintaining our unsealed roads

There are over 1800 km of roads in the Timaru District, 750km of which are unsealed. We spend approximately $1.3 million each year maintaining and renewing our unsealed roads.

This includes regular grading and the application of new metal as required to ensure a good surface for traffic to run on and to protect the structural integrity of the road.

Dust

Dust and loose surfaces are common on gravel roads, and there's not much we can do to prevent them, especially in hot, dry summer conditions. While there are some eco-friendly dust suppressant products available, these options are not economical to use under current council budgets and only offer short-term dust suppression.

Environment Canterbury has rules under the Canterbury Land and Water Regional Plan Rule regarding what is acceptable to use as a dust suppressant and how often it can be applied. If you wish to self-fund the application of dust suppressant on a section of road, this can be undertaken by council-approved contractors and with the approval of Council officers.

If you are interested in this, please refer to the Dust Suppressant on Road Application Form for conditions.  Applications should be filled out and submitted by emailing the completed form to roads@timd.govt.nz

• Dust Suppressant on Road Application (docx, 66.1 KB updated 22-Apr-2025)

Corrugations

Corrugations are among the more frustrating features of unsealed roads. They’re typically the result of poor driving behaviours like speeding, hard braking, and sharp cornering. While the Council’s contractor can smooth out some of the corrugations through grading, going too deep can damage the road’s substructure, allowing water to penetrate and leading to potholes, soft spots, and loose gravel.

Potholes

Potholes often form in low road areas, such as flat sections, hollows, or where corrugations exist. They develop when traffic displaces the fine materials that hold the road surface together. Within the limits of the available budget, the Council’s contractor maintains the road shape with a camber that suits the surrounding terrain and installs drainage cut-outs to direct water into the berm where feasible

Metalling

About 35,000 cubic metres of metal is placed on selected roads each year.  Roads with high traffic volumes can expect to be resurfaced more often than roads with lower traffic volumes, depending on available funding.

Maintenance, Grading and Metalling

By their nature, unsealed roads cannot be kept in a steady state.  Because they are made up of stones mixed with clay or silt fines, just how well they last between grading is very much dependent on the weather and volume of traffic.

Roads that carry heavy traffic, such as logging trucks and milk tankers, can also suffer increased wear.

Metalling and wearing course renewals typically occur between Spring and Autumn due to optimal pavement moisture conditions during those seasons. Metalling is avoided during the summer months, where possible, due to the increased risk of fine material loss. Roads with less traffic are graded less frequently, and those with more traffic may require more frequent grading.

The Council can advise when the grader is due. The road surface should remain in good condition for about a week and a half after grading, depending on weather conditions, traffic volumes and driver behaviour.

Monitoring and Inspection

Unsealed roads are inspected regularly by the Council staff and the Road Maintenance Contractor, who determines whether additional maintenance is required based on the level of service that the community can provide.

Corrugations caused by speeding motorists will generally not result in extra grading, whereas corrugations caused by bad weather or heavy traffic may.

Priority is given to the existing maintenance programme and areas that the contractor and council staff feel require extra attention based on the level of service required.  Council staff also monitor the contract and audit the standard of work completed.

Frequently asked questions

Last updated: 22 Apr 2025