1. P25 Specification for High Skid-Resistant Surfacings Joanna Towler, NZ Transport Agency Mark Owen, NZ Transport Agency Simon Fletcher, Fletcher Corporation Ltd 3rd International Surface Friction Conference, Safer Road Surfaces – Saving Lives, Gold Coast, Australia, 16 May 2011

2. Perceptions of High Skid Surfacings Durable binder and aggregate-based surfacings that provide high skid resistance That HSRS is not value for money $40 to $60/m 2 C.S. $2 - $8/m 2 ; A.C. $11 to $32/m 2 There are quality issues HSRS delaminates in a short period of time Substrate fails early Lack of skilled workforce

3. Whole of Life Costs In locations where: Natural aggregate polishes within 2 years Geometric improvements expensive or impractical High wet-road crash rate The whole of life costs may show that a HSRS is value for money

4. Case Study: SH2 Petone Overbridge

5. SH2 Petone Overbridge 15 – 20 Crashes/year Speed environment In 1997 calcined bauxite at $50/m 2 Post installation: 0.5 Crashes/year

6. 21 year history of injury accidents at SH2 Petone Overbridge Resurfacing – Open Graded Porous Asphalt (OGPA)

7. Calcined Bauxite laid 1997 Cost of resurfacing = $40,000 Annual crash savings = $1.9 million First year rate of return= 48 (B/C ≈ 400) At the time, the cost of applying calcined bauxite amounted to just two weeks’ crash savings.

8. P25 Specification P25 Specification for High Skid-Resistant Surfaces (HSRS)

9. P25 Summary of Performance Criteria The HSRS is required to achieve, for the defects liability period: the specified level of skid resistance (microtexture and macrotexture) the specified levels of material retention and adhesion to the substrate The substrate shall be strong enough to resist failure planes through the substrate

10. P25 Performance Criteria Skid Resistance0.65 ESCOver 95% of 10 m sections 0.6 ESCOver 100% of 10 m sections Texture0.9 mm MPD

11. P25 Performance Criteria Binder & Aggregate Retention/Loss < 0.25 linear mIn any 10 m section (both wheelpaths) < 0.15%In any 10 m section < 0.1%In any whole site

12. P25 Performance Criteria Visual Appearance binder and aggregate retention/loss cracking joint cracking

13. Binder overspill/underspill

14. Edges, Ridges and joins

15. P25 Performance Criteria Loose Aggregate< 150 g/m 2 In first 2 months of life < 50 g/m 2 From 2 months to end of Defects Liability Period

16. Specification Notes Apply to a completely bone-dry substrate Within the atmospheric moisture dew point tolerance On ‘as clean as possible’ substrate Apply resin binder to correct minimum thickness Avoiding laying on multi-layered chip seal (which has poor structural integrity). Strictly following all elements within the manufacturer’s Method Statement

17. P25 – Next Steps Currently out for industry sign-off Issue on NZTA website in next 6 weeks Next year we will do P33 Coloured Surfacing E-mail joanna.towler@nzta.govt.nz if you wish to review the current draftjoanna.towler@nzta.govt.nz Or visit us at the NZTA stand