Auckland Transport (AT) trialled 5 different pavement compositions along Old Woodcocks Road, Kaipara Flats, as part of our investigation into dust mitigation strategies for unsealed roads throughout the Northern Auckland region.
The dust suppression trials are now completed and the findings have been incorporated in the Unsealed Roads Improvement Framework. Please refer to the following for further information.
Please note that the Rodney dust suppression trial page will be archived on 30 June 2023.
AT is constructing 4 bound-and-sealed pavement surfaces and 1 unsealed surface on Old Woodcocks Road to investigate their effectiveness at reducing dust.
Through the trial, we aim to establish the local experience with different low-cost pavement types, identify how these pavements perform under uniform conditions, and establish whole-of-life costs of each pavement type.
Old Woodcocks Road has been selected as the trial site because the topography of the road is consistent and provides comparative sections of road to measure against.
Each trial section will be 300m long and clearly identified by both on-road markings and roadside signage.
Data will be collected from the trial sites including visual and physical dust monitoring, visual inspection of the pavement, cost and frequency of maintenance, and public feedback.
The results of the trial will be used to determine the suitability and best approach to introducing dust-suppressant solutions in the Auckland region.
- November 2016 - enabling work and construction of trial pavements.
- February 2017 - trial starts.
See a detailed map of the trial sites (JPG 84KB)
1. Chip seal over strengthened pavement
Conventional chip seal surface is constructed over lime/cement stabilised overlay. This option consists of thickening the existing pavement, strengthening through stabilisation, and the application of a conventional chip seal surface.
See a cross-section of the pavement at site 1 (PDF 164KB)
2. Chip seal over existing pavement
Conventional chip seal surface to be constructed over existing pavement. This is the cheapest sealed option on trial.
See a cross-section of the pavement at site 2 (PDF 164KB)
3. Notta Seal over existing pavement
A variation of the Otta seal. Similar preparation and application technique, but using higher quality metal and standard bitumen emulsion.
See a cross-section of the pavement at site 3 (PDF 164KB)
4. Otta seal over existing pavement
Otta seals originated in the Otta Valley of Norway as a means of providing a quick, economical, medium-term solution for unsealed roads that often became impassable over winter. This method is now used extensively overseas as a low-cost method of dust suppression or network extension.
See a cross-section of the pavement at site 4 (PDF 164KB)
5. Conventional MAP40 unsealed road
Conventional unsealed road, however, it is constructed with lower standard, weathered ‘brown rock’, MAP40, which is softer and typically crushes as it compacts, forming a tightly-bound unsealed surface.
See a cross-section of the pavement at site 5 (PDF 164KB)
6. Control section: Original unsealed pavement
Consisting of granular overlay on clay subgrade.
Pros and cons of sealed and unsealed pavements
Sealed pavement composition
- Low maintenance (life-cycle) cost.
- Minimal maintenance required.
- No dust nuisance.
- Safer driving conditions.
- Good ride quality.
- High capital cost.
- Longer construction period.
- Increased speed environment.
- Typically greater carriageway widths, hence increased impervious area and runoff.
Unsealed pavement composition
- Low capital cost.
- Reduced construction period.
- Reduced speed environment.
- High maintenance (life-cycle) cost.
- Regular maintenance required.
- Dust nuisance.
- Increased safety issues.
- Poorer ride quality.
Give us your feedback on the different trial pavements and help us identify the best dust-suppressant solution for unsealed roads.