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Geomteric road design standard for sealing low volume rural roads

  • 1.  Geomteric road design standard for sealing low volume rural roads

    Posted 6 days ago
    Edited by Charlette Newall 5 days ago
    ​Hi mates,

    I'm currently researching (for a study paper) the road design standards which are used when upgrading an unsealed low volume rural road to sealed. For my topic I've defined low volume as AADT <150 and <10% heavies.

    I would be interested to know what standard others use when upgrading low volume rural roads from unsealed to sealed.

    The Austroads Guide to Road Design Part 3: Geometric Road Design appears to be the most commonly referenced however I'd love to know if people are using this standard when upgrading existing rather than just for new construction. It appears the standard is based on an ideal scenario with no constraints. Even single lane rural roads require 8.7m carriageways. With financial and environmental constraints this is not always achievable or financially justified in very low volume environments.

    The new Austroads AP-R619-20 Network Design for Road Safety does not appear to include single lane rural roads either.

    Is there a requirement that every road, irrespective of traffic volume needs to be two lanes? Can anyone point me to where the research has been done to support this requirement? I'd love to understand the basis for the requirement in very low traffic environments where the chance of even seeing another vehicle almost nil. Understandably the ability for vehicles to pass each other is a road safety consideration, however does that requirement justify the entire road being that width?

    Thanks in advance



     



    ------------------------------
    Regards

    Charlette Newall
    Civil Assets Engineer
    Port Stephens Council
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    Pro Cert 2


  • 2.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 5 days ago
    Hi Charlette,
    Referring to Australian Standard AS1742.2 (2009) "Traffic control devices for general use" makes provisions for roads from 5.5m in width.
    5.3.3 in particular covers barrier lines with such applications as no overtaking zones on rural roads 5.5m or more wide where vertical and horizontal curves impact overtaking sight distance and makes a recommendation that roads less than 5.5m wide are widened to at least 5.5m over a section containing barrier lines.

    This would be considered for the delineation of the trafficable road pavement and does not include provisions for unsealed verges and overhead clearzones. Other safety considerations such as speed limits I suggest would also be a good idea where roads approach 5.5m.




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    Troy McGrath
    Asset Engineer
    Maitland City Council
    troy.mcgrath@maitland.nsw.gov.au
    0249349781
    ------------------------------

    Pro Cert 2


  • 3.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 5 days ago
    Hi Charlette

    IPWEAQ has published the Lower Order Road Design Guidelines that specify minimum standards for the design and construction of lower-order road assets (<150 VPD) and provide practitioners with a risk-based approach to capital improvements.

    Feel free to contact me to discuss further.

    Craig.Moss@ipweaq.com

    ------------------------------
    Craig Moss
    IPWEA (QLD) Division
    Fortitude Valley
    Australia
    ------------------------------

    Pro Cert 2


  • 4.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 4 days ago
    Hi Charlette,

    This is an interesting question, I want to know what you find out in this project!

    My understanding is that the Austroads Guide to Road Design is not intended to be used for urban local access design, or very low traffic volume rural roads. See Part 1 Section 1.3 - Application which states:

    The Guide addresses design practice across the range of road categories, from major roads to local roads,
    but does not address urban local-access roads. It also recognises that the design of roads should be based
    on the capabilities and behaviour of all road users, including pedestrians and cyclists, and on the
    performance and characteristics of vehicles. The different traffic mix and volumes, access requirements,
    functions and abutting developments that are typical of local roads create a different set of challenges that
    must be addressed in their own right. Additional guidance on the specific requirements of low trafficked roads
    is available in AASHTO (2001) and Giummarra (2001).

    I have found the Giummarra document here. With a quick read it seems the suggestion is to use 4m width for single lane roads.
    It seems that you have to purchase the AASHTO document. However, I have found a CODOT document that references the AASHTO document and specifies formation widths between 18 and 22 feet (~5.5 to 6.5m) for roads with AADT < 150.

    I hope this helps. Please let us know what you find out.

    ------------------------------
    Alex Dalrymple
    Clarence Valley Council
    Manager Civil Services
    Grafton
    Australia
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    Pro Cert 2


  • 5.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 4 days ago
    Hi Charlette
    IPWEAQ has published the Lower Order Road Design Guidelines that specify minimum standards for the design and construction of lower-order road assets and provide practitioners with a risk-based approach to capital improvements.

    This guideline is widely used across Queensland.

    As you are completing research for a study paper, I am happy to provide you with a complimentary copy and put you in touch with practitioners who can assist you with any practical questions.

    Please email me to follow up.

    ------------------------------
    Craig Moss
    Director, Professional Services
    IPWEAQ
    Craig.Moss@ipweaq.com
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    Pro Cert 2


  • 6.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 4 days ago
    Hi Charlette,

    The Austroads Guide to Road Design Part 1. Section 1.3 actually acknowledges that it is not intended for very low traffic volume rural roads or urban local access roads.
    ...Additional guidance on the specific requirements of low trafficked roads is available in AASHTO (2001) and Giummarra (2001).

    The AASHTO guide has to be purchased and would be in imperial units, but the Giummarra guide is available on the ARRB website. I have also found an extract from the AASHTO guide that specifies formation widths (inclusive of shoulders) between 18 and 22 feet (5.5 to 7m) for roads under AADT of 150.

    It would be good to see the outcome of your investigation.

    ------------------------------
    Alex Dalrymple
    Clarence Valley Council
    Manager Civil Services
    Grafton
    Australia
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    Pro Cert 2


  • 7.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 4 days ago
    Hi Charlette

    Earlier this year ARRB released a suite of Best Practice Guides (https://www.arrb.com.au/bestpracticeguides) specifically to assist local governments manage their road infrastructure. Of particular interest to you would be the Unsealed Roads guide, with Section 2.5.3 providing guidance on economic considerations of when to upgrade an unsealed road to sealed, based on AADT.

    Hopefully this helps, and please share the eventual paper with us all when it's published!

    Cheers,

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    Brett Williams
    City of Onkaparinga
    Senior Traffic & Transport Coordinator
    Noarlunga Centre
    Australia
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    Pro Cert 2


  • 8.  RE: Geomteric road design standard for sealing low volume rural roads

    Posted 4 days ago
    Charlette,

    The Austroads Guides are not particularly useful for low volume rural roads, hence the void filled by the IPWEAQ Publication "Lower Order Roads Design Guideline".  At Council there are policies in place that provide further guidance on the standard of road to be provided at low volumes.  If you are interested, search the Rockhampton Regional Council Website (About Council, Policies & Procedures, Roads & Drainage), and read the "Design Standards for Roads Guidelines" and "Upgrading of Unsealed Rural Roads to Sealed Standard Procedure".

    Regards,

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    Grant Vaughan
    Rockhampton Regional Council
    Manager Design Services
    ROCKHAMPTON
    Australia
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    Pro Cert 2