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This edition of Austroads News has a run down on the latest Austroads reports and upcoming seminars and conferences.

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Unlocking Freight Productivity with Faster Bridge Assessments

Austroads recently completed a project that developed a framework which could allow fast assessment of bridges using a simple line model comparison.

Improving freight productivity in Australia requires better access to the road network for heavy vehicle operators. Bridge capacity assessment is critical in this process.

The framework allows each bridge to be assessed by a managing jurisdiction against a set of nationally consistent loading service levels. Each loading service level consists of a loading configuration including a primary reference vehicle and co-existing vehicles. Load effects are calculated and compared to the bridge capacity to determine the maximum loading service level that the bridge can safely withstand.

It is envisaged that the system would be administrated through a web interface, hosted by the National Heavy Vehicle Regulator, allowing 24 hour access to the permitting system and rapid issuing of singular permits for multiple jurisdictions. This immediate feedback will allow applicants to fine tune their vehicle configuration and can allow for route optimisation.

This project focussed on developing the framework, which has produced encouraging results. The next stage of work will be to set service levels and select reference vehicles, configurations and associated load factors with the jurisdictions.

Austroads Bridge Conference - Register now

The Austroads Bridge Conference will be held in Sydney at the ANZ Stadium, Olympic Park from Wednesday 22 October to Friday 24 October 2014, with a half-day technical tour planned for Saturday 25 October.

With 115 papers accepted and speakers from 12 countries, the event is shaping up to be an unmissable opportunity for bridge practitioners. 

For more information and registration visit www.abc2014sydney.com.au

This conference will be held in conjunction with the 26th ARRB Conference.

Good Practice in Reseal Programming

This report provides asset managers with practical guidance in the development and delivery of effective resealing programs. It builds on accumulated experience of previous studies and a review of sprayed seal performance throughout Australasia.

Sprayed seal treatments constitute the highest percentage of the sealed road networks in Australia and New Zealand.  These treatments have been found to be a cost-effective way of preserving the life of a road pavement and providing a safe and smooth running surface.  Accordingly, positive asset management (technical), road safety and community outcomes can be accrued from sprayed seal programs.

While an extensive body of sprayed seal knowledge and experience exists, there are significant issues which have serious consequences for the state and sustainability of road surfacings, and pavement assets, and ultimately their safe and efficient use.  Examples of good practice do exist and road agencies are encouraged to review their procedures and the capabilities of their systems and human resources, with a view to adopting good practice and building capability.

Specific areas requiring attention include:

  • Definition of a level of service (LOS) framework, with the safety of the public as a prime concern, including: identifying and responding to road hazards, including potholes; managing skid resistance to within appropriate levels; and managing roughness levels and rut levels to minimise the risk of loss of vehicle control.
  • Placing greater emphasis on understanding the consequences of budget constraints as this is a key issue with many agencies.

Hot Storage of PMB May Not Reduce On-road Performance

Polymer modified binders (PMBs) are increasingly used in road construction as they provide enhanced performance properties, such as resistance to permanent deformation and low temperature cracking, compared with conventional bitumen. They are produced by blending bitumen with materials such as synthetic or natural polymers, or crumb rubber obtained from the recycling of vehicle tyres.

Even though PMBs show enhanced service properties, a number of studies have indicated that their test properties degrade or change during hot storage.

This study investigated the effects of hot storage on the conventional test properties and field performance of PMBs containing low (3.5% by weight) and high (6% by weight) levels of styrene-butadiene-styrene (SBS) polymer. The chemical changes that occurred in the PMBs during storage were also studied.

The study found that even though the polymer in both PMBs was degrading during storage there was no change in the wheel tracking performance of the PMB containing 6% SBS in asphalt for storage periods up to five days. The wheel tracking performance of the PMB containing 3.5% SBS in asphalt was also better after two and four days of storage than after no days of storage. The fatigue performance of both PMBs in asphalt also improved when the materials were stored.

The results obtained in this study appear to indicate that degradation of the polymer in a PMB during hot storage may not necessarily reduce the performance of material on the road.

Based on the information available to date, it does not appear fruitful to include a PMB degradation test in the Australian PMB specification at the current time which ranks SBS-based PMB binders in terms of their resistance to polymer degradation during hot storage.

New LTPP Sites Established in South Australia

Austroads established its long-term pavement performance (LTPP) project in 1995. The LTPP study involves monitoring the performance of various types of in-service pavements in different climatic and traffic environments to account for the range of variables influencing pavement performance.

Over the last few years, a significant number of sites have been removed from the study due to pavement rehabilitation and road improvement programs.

In September Austroads published a report detailing two replacement test sections of pavement in South Australia: the Port River Expressway (PRExy), Port Adelaide; and the Dukes Highway, Cooke Plains.

The report contains detailed information about the sites including:

  • surface deflection, longitudinal and transverse profile, and visual assessment data collected during initial fieldwork in November 2013 as part of the 2013–14 LTPP monitoring program, and
  • traffic data, pavement composition, historic pavement performance and maintenance activities, provided by the South Australian Department of Planning, Transport and Infrastructure (DPTI).

Mobile Surface Wear Rig Undergoes First Trials

The horizontal shear stresses applied to pavement surfacings by new configurations of freight vehicles are not yet known.

Austroads has released a report detailing the first suite of testing activities undertaken with a mobile pavement surface wear rig developed by ARRB.  The rig has been designed to gain an improved understanding of the failure mechanisms particular to the pavement surface layer that may be caused by changing axle configurations and the loadings applied by freight vehicles. 

Existing pavement wear models, such as the 4th power law, are only applicable to pavement deflections due to increases in vertical loading. Models need to be developed that can be used to predict the horizontal stresses applied by next generation freight vehicles and the resulting pavement surface wear. This information will be used in incremental pricing and mass-distance charging of heavy vehicles.

The testing phase of this project will continue in 2014–15.

Inspections Reveal Seal Trials Generally Performing Well

Austroads has published a report detailing the latest results of the seal trials in Victoria, New South Wales and South Australia.

The trials reported on include:

  • a non-modified binders trial near Gisborne, Victoria and
  • two polymer modified binder (PMB) trials near Coober Pedy, South Australia and Cooma, New South Wales.

The non-modified binders trial near Gisborne is designed to investigate the performance of a more viscous grade of bitumen in sprayed seals. After seven years of life, the seals in the trials are performing well with little sign of distress.  There are small and isolated incidences of crocodile cracking, which is caused by a failure in the pavement, as well as some unsound and broken aggregate, but very little stripping or flushing.

The objective of the PMB trials is to validate and rank the performance of PMB sprayed seal binders as a crack inhibitor and as a seal. After two years the PMB trials were performing well in all cases at the Coober Pedy site, but showing signs of distress in some sections at Cooma. 

Double/Double Primerseals Performing Well

SprayLine has been constructing double/double primerseals with crumb rubber modification on a variety of sites in Victoria. It is not typical practice to use two-layer primerseals, or polymer modification in primerseals, and methods to do so are not described by Austroads specification or guidance documents.

Austroads engaged the ARRB Group to inspect seven double/double primerseal sites in Victoria and rate their performance.

The broad concept of double/double primerseals was adapted by Sprayline from shoulder sealing practices observed in South Australia.

Unmodified binders such as C170 have been used for double/double primerseals, and are used with a small amount of cutter.

The seals all use crumb rubber modified binders, to improve the hardiness and stress resistance of the seal compared to a non-modified binder.

The double/double primerseals inspected were found to be performing well, and providing a viable option for an initial seal over a pavement where stresses can be expected to be higher than ideal for a typical single/single primerseal.

Assessing Fitness to Drive Update

Assessing Fitness to Drive provides guidance for health professionals and driver licencing bodies on the health assessment of private and commercial drivers of heavy vehicles, light vehicles and motorbikes.

The National Transport Commission has recently provided a correction to Figure 7B: Bruce protocol nomogram for women on page 41 and updated the contact details for the Tasmanian Medical Review Officer on page 149.

A corrigendum, which outlines the changes, can be downloaded as a PDF.

An updated electronic edition of Assessing Fitness to Drive for Commercial and Private Vehicle Drivers can be downloaded from the Austroads publications website. An updated hard copy will not be provided but future purchases will include the corrigendum.

Upcoming Workshops and Conferences

26th ARRB Conference 
19-22 October 2014, Sydney Australia

Austroads Bridge Conference 
22-24 October 2014, Sydney, Australia

Walk 21
21-23 October 2014, Sydney, Australia

NEW 2nd REAAA Business Fourm
23 October 2014, Sydney, Australia

NEW ALGA National Local Roads and Transport Congress
12-14 November 2014, Tamworth, Australia

10th International Conference on Transport Survey Methods
16-21 November 2014, Leura, Australia

Engineers Australia Convention 2014
24-28 November 2014, Melbourne, Australia

NEW International Road Federation and Roads Australia Regional Conference (Abstracts deadline 30 Nov 2014)  
4-7 May 2015, Sydney, Australia

 XXVth World Road Congress Call for papers
2-6 November 2015, Seoul, Korea