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Cover of Creating Consistent Speed Terminology in Austroads Guide to Road Design
Creating Consistent Speed Terminology in Austroads Guide to Road Design
  • Publication no: AP-R768-26
  • ISBN: 978-1-923617-61-2
  • Published: 6 July 2026

The purpose of this report is to assess how speed terms are used across various Parts of the Austroads Guide to Road Design (AGRD) and to recommend clear, consistent definitions for these terms.

In addition, the report reviews other key Austroads Guides and international references, and recommends aligning terminology across the AGRD, the Guide to Traffic Management (AGTM), and the Guide to Road Safety (AGRS).

The report addresses existing inconsistencies by recommending standard definitions – particularly for design speed, operating speed and desired speed – and by proposing updates to relevant sections of the AGRD. Definitions are also provided for: target speed, limiting device speed and limiting curve speed.

  • 1. Introduction
    • 1.1 Purpose
    • 1.2 Scope
    • 1.3 Methodology
  • 2. Speed Terms Defined in the AGRD
    • 2.1 Design Speed
      • 2.1.1 Definition of Design Speed in the AGRD
      • 2.1.2 Definition of Design Speed in the Green Book
      • 2.1.3 Definition of Design Speed in the Canadian Design Guide
      • 2.1.4 Definition of Design Speed in the AS 1742
      • 2.1.5 Definition of Design Speed in the Austroads Glossary of Terms
      • 2.1.6 Recommended Definition
    • 2.2 Desired Speed
      • 2.2.1 Definition of Desired Speed in the AGRD
      • 2.2.2 Definition of Desired Speed in the Canadian Design Guide
      • 2.2.3 Definition of Desired Speed in the AS 1742
      • 2.2.4 Definition of Desired Speed in the Austroads Glossary of Terms
      • 2.2.5 Recommended Definition
    • 2.3 Operating Speed
      • 2.3.1 Definition of Operating Speed in the AGRD
      • 2.3.2 Definition of Operating Speed in the Green Book
      • 2.3.3 Definition of Operating Speed in the Canadian Design Guide
      • 2.3.4 Definition of Operating Speed in the AS 1742
      • 2.3.5 Measuring the 85th Percentile Speed
      • 2.3.6 Definition of Operating Speed in the Austroads Glossary of terms
      • 2.3.7 Recommended Definition
    • 2.4 Target Speed
      • 2.4.1 Target Speed Used in the AGRD
      • 2.4.2 Target Speed Used in the Green Book
      • 2.4.3 Conclusion
    • 2.5 Other Speed Terms Defined in the AGRD
      • 2.5.1 Definition of the Limiting Curve Speed Used in the AGRD
      • 2.5.2 Definition of the Limiting Device Speed
      • 2.5.3 Definition of the Speed Environment in the AGRD
  • 3. Speed Terms Defined in the AGTM
    • 3.1 Running Speed
      • 3.1.1 Running Speed in the AGTM
      • 3.1.2 Running Speed Used in the Green Book
      • 3.1.3 Running Speed Used in the Canadian Design Guide
      • 3.1.4 Recommendation on the Use of Running Speed in the AGRD
    • 3.2 Target Speed Used in the AGTM
    • 3.3 Other Speed Definitions in the AGTM
  • 4. Speed Terms Defined in the AGRS
    • 4.1 Traffic Speed and Travel Speed
    • 4.2 Speed Environment
  • 5. Relationship Between Speed Measures
    • 5.1 Operating Speed Model
      • 5.1.1 Section Operating Speed
      • 5.1.2 Operating Speed Evaluation
  • 6. Operating Speed or Design Speed?
    • 6.1 AGRD Text Where Design Speed Would be Appropriate
      • 6.1.1 AGRD Part 3
      • 6.1.2 AGRD Part 6
    • 6.2 Use of Design Speed in Other Austroads Guides
      • 6.2.1 Design Speed References in the AGTM
      • 6.2.2 Design Speed References in the AGRS
    • 6.3 Use of Design Speed in Other Guides
      • 6.3.1 Design Speed References in the AS1742
  • 7. Use of Operating Speed
    • 7.1 AGRD Text Where Operating Speed Would be Appropriate
      • 7.1.1 AGRD Part 3
      • 7.1.2 AGRD Part 6
    • 7.2 Use of Operating Speed in Other Guides
      • 7.2.1 Use of Operating Speed in AGTM that is Consistent with the Recommended Definitions
      • 7.2.2 Use of Speed Terms in AGTM that are Inconsistent with the Recommended Definitions
      • 7.2.3 Use of Operating Speed in AGRS that is Consistent with the Recommended Definitions
  • 8. Use of Desired Speed
    • 8.1 Use of Desired Speed in AGRD
    • 8.2 Use of Desired Speed in Other Guides
      • 8.2.1 Uses of Desired Speed in the AGTM that are Consistent with the Recommended Definitions
      • 8.2.2 Use of Desired Speed in AGTM that are Inconsistent with the AGRD Recommended Definitions
      • 8.2.3 Use of Desired Speed in AGRS that is Consistent with the Recommended Definitions
  • 9. Other Speed Terms Used in the AGRD
    • 9.1 Travel Speed and Traffic Speed
      • 9.1.1 Replacing Travel Speed and Traffic Speed with Operating Speed
      • 9.1.2 Replacing Travel Speed and Traffic Speed with Design Speed
      • 9.1.3 Other Examples
    • 9.2 Speed Environment
      • 9.2.1 Replacing Speed Environment with Operating Speed
      • 9.2.2 Replacing Speed Environment with Design Speed
      • 9.2.3 Replacing Speed Environment with Desired Speed
      • 9.2.4 Other Possible Replacement of Speed Environment with Another Term
    • 9.3 Limiting Curve Speed
  • 10. Other Speed Terms Used in the AGTM and the AGRS
  • 11. Conclusions and Recommendations
    • 11.1 Recommended Definitions
    • 11.2 Speed Terms Defined in the AGTM and AGRS
    • 11.3 Relationship Between the Speed Terms
    • 11.4 Recommended Changes to the AGRD
  • References
  • Appendix A Speed References in the AGRD
    • A.1 Texts Where Design Speed is Considered to be More Appropriate
      • A.1.1 Comments on AGRD Parts 1, 3, 4, 4A, 4B, 4C, 5, 5A and 5B
      • A.1.2 Comments on AGRD Part 6
      • A.1.3 Comments on AGRD Parts 6A, 6B and 7
    • A.2 Texts Where the Use of Operating Speed Type is Appropriate
    • A.3 Texts Containing Speed References
      • A.3.1 Applicability of the Term ‘Travel Speed’ in the AGRD
      • A.3.2 Applicability of the Term ‘Traffic Speed’ in the AGRD
      • A.3.3 Applicability of the Term ‘Speed Environment’ in the AGRD
      • A.3.4 Applicability of the Term ‘Limiting Curve Speed’ in the AGRD
      • A.3.5 Applicability of the Other Speed Terms used in Parts 3 and 6 of the AGRD
  • Appendix B Speed References in the AGTM
    • B.1 Texts in AGTM with Acceptable References to Operating, Design and Desired Speed
    • B.2 Use of Operating, Design and Desired Speed that is inconsistent with the AGRD
      • B.2.1 Operating, Design and Desired Speed References in AGTM Parts 1 to 4
      • B.2.2 Operating, Design and Desired Speed References in AGTM Parts 5 to 8
      • B.2.3 Operating, Design and Desired Speed References in AGTM Parts 9 to 13
    • B.3 Other Speed References Used in the AGTM
  • Appendix C Speed References in the AGRS
    • C.1 Texts in AGRS with Acceptable References to Operating, Design and Desired Speed
    • C.2 Other Speed References Used in the AGTM
  • Appendix D Section 2.3.6 of the US Green Book
  • Appendix E Speed Guidance in UK Documents
    • E.1 CA 185: Vehicle Speed Measurement – Free Flow Conditions
    • E.2 Director of Engineering Memorandum DEM 118/16: Design Speed for Roads
  • Appendix F References to Speed in the Australian MUTCD
    • F.1 85th Percentile speed
      • F.1.1 Definition of the 85th Percentile Speed
      • F.1.2 Use of the 85th Percentile Speed
    • F.2 Design Speed
      • F.2.1 Definition of Design Speed
      • F.2.2 Use of Design Speed
    • F.3 Operating Speed
      • F.3.1 Definition of Operating Speed
      • F.3.2 Use of Operating Speed
    • F.4 Desired Speed
      • F.4.1 Definition of Desired Speed
      • F.4.2 Use of Desired Speed
    • F.5 Approach Speed
      • F.5.1 Definition of Approach Speed
      • F.5.2 Use of Approach Speed
    • F.6 Speed Environment
      • F.6.1 Definition of Speed Environment
      • F.6.2 Use of Speed Environment
    • F.7 Other Speed Definitions in AS1742.0
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