Austroads Publications Online


Guide to Road Design Part 6: Roadside Design, Safety and Barriers

Log in or Register to Download free PDF

Publication no: AGRD06-10 Pages: 294

Guide to Road Design Part 6: Roadside Design, Safety and Barriers provides an introduction to roadside design and guidance on roadside safety and the selection and use of road safety barrier systems.

Roadsides have to accommodate many features that support the road and the safe and efficient operation of traffic, and have to be designed with regard to environmental requirements.

Part 6 provides information to enable designers to understand principles that lead to the design of safe roads, identify hazards, undertake a risk assessment process of roadside hazards, establish the need for treatment of hazards and determine the most appropriate treatment to mitigate hazards. A comprehensive design process, guidance and design considerations are provided for the selection of a suitable road safety barrier and for the lateral and longitudinal placement of road safety barrier systems.


Table of Contents

1 Introduction
  • 1.1 Purpose
  • 1.2 Scope of this Part
  • 1.3 Road Safety
  • 1.3.1 Providing for a Safe System
  • 1.3.2 Contribution of Roadside Design to Road Safety
  • 1.4 Terminology
2 Roadside Design
  • 2.1 General
  • 2.2 Roadside Facilities and Infrastructure
  • 2.2.1 Part 6: Roadside Design, Safety and Barriers
  • 2.2.2 Part 6A: Pedestrian and Cyclist Paths
  • 2.2.3 Part 6B: Roadside Environment
3 Designing for Safety
  • 3.1 General
  • 3.2 A Safe Road Environment
  • 3.3 Design for Risk Reduction
  • 3.3.1 Reduce Inherent Hazard
  • 3.3.2 Prevent an Incident
  • 3.3.3 Limit Damage
  • 3.4 Design to Keep Vehicles on the Road
  • 3.4.1 General
  • 3.4.2 Combining Design Parameters and Consistent Design
4 Design to Mitigate Hazards
  • 4.1 Hazard Mitigation Process
  • 4.2 Design Step D1: Determine Area of Interest
  • 4.2.1 General
  • 4.2.2 Determine the Clear Zone
  • 4.2.3 Application of Clear Zones to Design
  • 4.3 Design Step D2: Identify Hazards
  • 4.3.1 General
  • 4.3.2 Types of Hazards
  • 4.3.3 Embankment Warrant for High-speed Roads
  • 4.3.4 Embankment Assessment Process
  • 4.3.5 High-consequence Hazards
  • 4.4 Design Step D3: Identify Treatment Options
  • 4.5 Design Step D4: Evaluation of Treatment Options
  • 4.5.1 General
  • 4.5.2 Quantitative Assessment
  • 4.5.3 Qualitative Assessment
  • 4.5.4 Methods for Quantitative Analysis
  • 4.5.5 Simple Manual Method
  • 4.5.6 Detailed Manual Method
  • 4.5.7 Roadside Impact Severity Calculator
  • 4.5.8 Roadside Safety Analysis Program
  • 4.5.9 Alternative Crash Risk Method
  • 4.6 Hazard Risk Assessment
  • 4.6.1 General
  • 4.6.2 Risk Step R1 – Calculate the Frequency of Errant Vehicle Crashes
  • 4.6.3 Risk Step R2 – Determine the Severity Index
  • 4.6.4 Risk Step R3 – Calculate Crash Cost for Hazard
  • 4.7 Design Step D5: Rank Treatment Options and Recommend Preferred Action
  • 4.8 Design Step D6: Design the Roadside Treatments
5 Treatment Options
  • 5.1 General
  • 5.2 Summary of Treatment Options
  • 5.3 Effectiveness of Treatment Options
  • 5.4 Types of Treatments
  • 5.4.1 Treatments for Trees
  • 5.4.2 Treatments for Steep Downgrades
  • 5.4.3 Treatments for Medians
  • 5.4.4 Treatments for Verges
  • 5.4.5 Treatments for Drains
  • 5.4.6 Treatments for Drainage Features
  • 5.4.7 Treatments for Fill Slopes
  • 5.4.8 Treatments for Rock Face Cuttings
  • 5.4.9 Treatments for Roadway Improvements
  • 5.4.10 Treatments for Watercourses, Canals and other Bodies of Water
  • 5.4.11 Treatments for Minor Roadside Hazards
  • 5.4.12 Treatments for Road Furniture
  • 5.4.13 Treatments for Poles
  • 5.4.14 Road Safety Barriers
  • 5.4.15 Road Safety Barriers on Corners of Intersections
  • 5.4.16 Treatments at Level Crossings
  • 5.4.17 Weather Warning Systems
6 Road Safety Barriers
  • 6.1 Introduction
  • 6.1.1 General
  • 6.1.2 General Requirements for Road Safety Barrier Systems
  • 6.2 Factors Considered in Barrier Selection
  • 6.2.1 Site Conditions
  • 6.3 Road Safety Barrier Design Process
  • 6.3.1 Outline of Process
  • 6.3.2 Step B1 – Collect Site Information
  • 6.3.3 Step B2 – Determine the Objectives of the Safety Barrier
  • 6.3.4 Step B3 – Determine the Lateral Position of the Barrier
  • 6.3.5 Offset to Travel Lane
  • 6.3.6 Support Width
  • 6.3.7 Deflection Width
  • 6.3.8 System Width
  • 6.3.9 Barrier Location in Medians
  • 6.3.10 Narrow Medians
  • 6.3.11 Wider Medians
  • 6.3.12 Step B4 – Determine the Barrier-to-hazard Clearance
  • 6.3.13 Step B5 – Determine the Barrier Containment Level Required
  • 6.3.14 Step B6 – Choose the Barrier Type
  • 6.3.15 Step B7 – Determine Dynamic Deflection
  • 6.3.16 Step B8 – Determine Vehicle Roll Allowance and System Width
  • 6.3.17 Step B9 – Determine the Working Width
  • 6.3.18 Step B10 – Check that the Working Width is Less than the Barrier-to-hazard Clearance
  • 6.3.19 Step B11 – Determine Barrier Points of Need
  • 6.3.20 Step B12 – Check that the Minimum Length of Barrier is Provided
  • 6.3.21 Step B13 – Check Sight Distance
  • 6.3.22 Step B14 – Choose Terminal Treatments
  • 6.3.23 Step B15 – Design the Transitions Between Barriers
  • 6.3.24 Step B16 – Confirm that the Barrier Meets the Objectives
  • 6.4 General Access Through Road Safety Barriers
  • 6.5 Road Safety Barriers for Vulnerable Road Users
  • 6.5.1 Motorcyclists
  • 6.5.2 Pedestrians and Cyclists
  • 6.6 Aesthetic Road Safety Barriers
  • 6.7 Other Road Safety Barrier Design Considerations
  • 6.7.1 Barriers at Intersections
  • 6.7.2 Orientation to Travel Lanes
  • 6.7.3 Stepped Offset
  • 6.7.4 Excessive Offset
  • 6.7.5 Delineation
  • 6.7.6 Minimum Curve Radius for Wire Rope Barriers
  • 6.7.7 Foundations
  • 6.7.8 System Height
  • 6.7.9 Blockouts on Steel Rail Systems
7 Design for Steep Downgrades
  • 7.1 Purpose and Need
  • 7.2 Containment Facilities
  • 7.2.1 Gravity Safety Ramp
  • 7.2.2 Arrester Beds
  • 7.2.3 Dragnets
  • 7.3 Warrant for Investigation
  • 7.4 Location and Spacing
  • 7.5 Key Design Considerations
  • 7.6 Design Process
  • 7.6.1 Outline of Process
  • 7.6.2 Step S1 – Determine Vehicle Entry Speed
  • 7.6.3 Step S2 – Evaluate Truck Stability on Approach
  • 7.6.4 Step S3 – Design Entry Alignment
  • 7.6.5 Step S4 – Determine Type of Facility
  • 7.6.6 Step S5 – Determine Pavement Surface of Facility
  • 7.6.7 Step S6 – Design Facility Length
  • 7.6.8 Step S7 – Design the Facility
  • 7.6.9 Step S8 – Design End Treatment
  • 7.6.10 Step S9 – Design Vehicle Recovery Facilities
  • 7.6.11 Step S10 – Design Delineation
  • 7.6.12 Step S11 – Design Truck Parking Areas
References
Appendix A Terminology
  • A.1 General Terms
  • A.1.1 Key Words
  • A.1.2 Other General Engineering and Road Safety Terms
  • A.1 Expression of Slopes
  • A.2 Vehicle Movement Terminology
  • A.3 Road Safety Barrier Terminology
  • A.4 Working Width and Dynamic Deflection
Appendix B Hazard Mitigation Worksheet
Appendix C RTA Method
  • C.1 Process
  • C.2 Hazard Corridor Width
  • C.3 Method
  • C.4 Plot the Hazard Corridor
  • C.5 Background to the Hazard Corridor Width
Appendix D Examples of Clear Zone Calculations
  • D.1 Example 1
  • Discussion
  • D.2 Example 2
  • Discussion
  • D.3 Example 3
  • Discussion
  • D.4 Example 4
  • Discussion
Appendix E Severity Indices Tables
Appendix F Example of Manual Calculation of Run-off-road Crash Numbers and Costs
  • F.1 Example
  • F.2 Run-off-road Crashes into Hazard
  • R1 – Calculate the frequency of errant vehicle crashes
  • F.3 Options for Treatment
Appendix G RISC Method and Process
  • G.1 Roadside Impact Severity Calculator (RISC)
  • G.1.1 Determine Road Environment Variables
  • G.1.2 Determine Traffic Volumes
  • G.1.3 Determine Curvature and Grade Factors
  • G.1.4 Identify Roadside Object Attributes
  • G.1.5 Calculate Encroachment Frequency
  • G.1.6 Calculate Object Collision Frequency
  • G.1.7 Determine Severity Index (SI) for Object
  • G.1.8 Determine Crash Costs
Appendix H Treatments for Brownfield Sites
  • H.1 Treatments for Roads
  • H.1.1 Treatments for Pavement Edge Drop-off
  • H.1.2 Treatments for Opposing Vehicles
  • H.2 Treatments for Bridges
  • H.2.1 General
  • H.2.2 Treatments for Bridge Piers, Abutments, End Posts and Tunnel Portals
  • H.3 Barrier Placement in Constrained Situations
  • H.3.1 Location on Embankments
  • H.3.2 Location on Urban Footway Corners
  • H.4 Wire Rope Barrier in Narrow Medians
Appendix I Examples of Length of Need Calculations
  • I.1 General
  • I.2 Run-out Length Method
  • I.3 Angle of Departure Method
  • I.4 Worked Examples to Determine Road Safety Barrier Length of Need
  • I.4.1 Example 1
  • I.4.2 Example 2
Appendix J Types of Safety Barrier Terminals
  • J.1 General
  • J.1.1 Specific Gating End Treatments
  • J.1.2 Non-gating End Treatments
  • J.1.3 Trailing Terminal
Appendix K Transitions Between Barrier Types
  • K.1 General
  • K.2 Design Criteria – Physically Connected Barriers
  • K.3 Typical Interfaces between Barrier Types
  • K.3.1 General
  • K.4 W-beam to Thrie-beam
  • K.5 W-beam to Concrete
  • K.6 Thrie-beam to Concrete
  • K.7 Wire Rope Safety Barrier to Semi-rigid Barrier
  • K.8 Wire Rope Safety Barrier to Concrete Barrier
Appendix L Barriers at Intersections
Commentary 1
Commentary 2
  • C2.1 Combinations of Design Parameters
  • C2.2 Consistent Design Environment
  • C2.3 Vehicle Mix Considerations
  • C2.4 Other Factors Contributing to Errant Vehicles
Commentary 3
  • C3.1 Background to Clear Zone Width and Hazard Corridor Width
Commentary 4
Commentary 5
  • Point hazards
  • Continuous hazards
Commentary 6
Commentary 7
Commentary 8
Commentary 9
Commentary 10
Commentary 11
Commentary 12
  • C12.1 General
  • C12.2 Vehicle Trajectory Over Embankments
  • C12.3 Vehicle Trajectory Over Kerbs
  • C12.4 Vehicle Trajectory Over Cutting Slopes
  • C12.5 Summary of Limitations on Barrier Location
Commentary 13
Commentary 14
Commentary 15

This website is operated by CanPrint Communications on behalf of Austroads. If you have any questions, please use the feedback form or call us on 1300 889 873, between 8:00 am and 5:00 pm AEST. If you are outside Australia please call us on +61 2 6293 8381.

Terms of Use