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AGRS08-15
Detailed Case Study
Summarising the Factors Identified from the Crash Listings, Factor Matrix and Collision Diagram
Road safety
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Table of Contents
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Table of Contents
1. Introduction
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1.1 Purpose of the Guide
1.2 Changes in this Edition
1.3 Risk Assessment and Management: Linking ‘Reactive’ and ‘Proactive’ Safety Approaches
1.4 Developing a Program to Address High Crash Risk Locations
1.5 Taking Action to Improve Road Safety
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1.5.1 The Countermeasure Approach and the Role of Infrastructure
1.5.2 The Safe System Approach
1.5.3 Crash Risk
1.5.4 What is a Crash Location?
1.5.5 Treating Crash Locations
1.5.6 Who Should Investigate Crash Locations and Develop Solutions?
1.5.7 What are road safety engineering skills?
1.6 How to Use this Guide
1.7 Steps in the Crash Location Treatment Process
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1.7.1 The Steps
2. Road Crash Data
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2.1 Importance of Crash and Road Data
2.2 Data Sources and Codes
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2.2.1 Minimum Reporting and Coding Criteria
2.3 Sources of Crash Data
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2.3.1 Purposes of data collection
2.4 Technology Available for Data Collection
2.5 Limitations and Accuracy of Crash Data
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2.5.1 Coding of crash types – DCAs, RUMs and VMCs
3. Identifying Crash Locations
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3.1 Defining the Locations
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3.1.1 Deciding on a Time Period
3.1.2 Criteria for Selecting Locations to Investigate for Countermeasures
3.1.3 Using a Threshold Method
3.1.4 Chance Variation
3.2 Intersections
3.3 Routes
3.4 Areas of the Road Network
3.5 Mass Action
4. Diagnosing the Crash Problem and Selecting Treatments
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4.1 Analysis of Crash Data and Interpretation
4.2 Other Relevant Information
4.3 Site Investigation
4.4 Identification of Crash Causation and Crash Severity Factors
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4.4.1 Applying the Process to Area Studies and Mass Action Programs
4.5 Countermeasure Selection and Design
4.6 Crash Modification Factors
4.7 Implementing the Treatment
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4.7.1 Designing a Safe Remedial Treatment
4.7.2 Implementing the Treatment
5. Economic Appraisal
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5.1 Objectives
5.2 Cost of Crashes and Remedial Treatment Options
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5.2.1 Treatment Options
5.2.2 Cost of Crashes
5.3 Calculating the Costs and Benefits
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5.3.1 Key Parameters
5.3.2 Discounting
5.3.3 Calculating Costs and Benefits
5.4 Ranking the Treatment of Crash Locations
5.5 Presenting the Results
5.6 Applying to Routes, Areas and Mass Actions
5.7 Post-completion Evaluation
5.8 Alternatives to Benefit Cost Approach
6. Monitoring and Evaluation
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6.1 Purpose
6.2 Monitoring and Evaluation Methods
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6.2.1 Statistical Analysis
6.3 Issues for Consideration
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6.3.1 Planning before Treatment for Monitoring Afterwards
6.3.2 Threats to the Validity of Evaluation
7. Preparing a Crash Report
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7.1 Structure
References
Appendix A Pillars of a Safe System
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Appendix A 1 Safe Speeds
Appendix A 2 Safe People
Appendix A 3 Safe Roads and Road Environments
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Appendix A 3.1 What is a safe road environment?
Appendix A 3.2 Safe intersections
Appendix A 3.3 Safe non-intersection locations
Appendix A 3.4 Design of devices
Appendix A 4 Safe Vehicles
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Appendix A 4.1 Manoeuvrability
Appendix A 4.2 Visibility
Appendix A 4.3 Cornering characteristics
Appendix A 4.4 Braking characteristics
Appendix B Crash Codes for Australian Jurisdictions
Appendix C Example Blank Factor Matrix Form
Appendix D Examples
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Appendix D 1 Practical Example 1: Investigation of High Crash Locations
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Appendix D 1.1 Example 1A
Appendix D 1.2 Example 1B
Appendix D 1.3 Example 1C
Appendix D 1.4 Example 1D
Appendix D 2 Practical Example 2: Chance Variation
Appendix D 3 Practical Example 3: Writing a Preliminary Report
Appendix D 4 Practical Example 4: Applying Crash Modification Factors
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Appendix D 4.1 Example 4A
Appendix D 4.2 Example 4B
Appendix D 5 Practical Example 5: Road Safety Audit of a Remedial Treatment
Appendix D 6 Practical Example 6: Selecting the Countermeasures
Appendix D 7 Practical Example 7: Economic Appraisal
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Appendix D 7.1 Example 7A: (based on Ogden 1996)
Appendix D 7.2 Example 7B (based on Andreassen 1992a, p.5)
Appendix D 8 Practical Example 8: Monitoring
Appendix E Detailed Case Study
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Appendix E 1 Step-by-step process in the Investigation and Treatment Process
Appendix E 2 Obtaining all the Relevant Information
Appendix E 3 Constructing a Factor Matrix and Identifying Common Factors and Clustering of Crashes
Appendix E 4 Drawing a Collision Diagram and Identifying Clusters of Crash types at Locations
Appendix E 5 Summarising the Factors Identified from the Crash Listings, Factor Matrix and Collision Diagram
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Appendix E 5.1 Intersections
Appendix E 5.2 Road Sections
Appendix E 5.3 Summary of Factors
Appendix E 6 Inspecting the Site
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Appendix E 6.1 Observations from Driving the Site
Appendix E 6.2 Observations from inspecting the site on foot
Appendix E 6.3 Observed Driver Behaviour
Appendix E 6.4 Confirm Speed Limit
Appendix E 6.5 Discussion
Appendix E 7 Selecting the Countermeasures
Appendix E 8 Designing a Safe Remedial Treatment
Appendix E 9 Economic Appraisal
Appendix F Crash Modification Factors
Appendix G Confidence Limits and Changes in Critical Mean
Appendix H Monitoring Techniques and Allowing for Regression-to-the-mean
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Appendix H 1 Monitoring Techniques
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Appendix H 1.1 Experimental Design
Appendix H 1.2 Before and After Studies
Appendix H 1.3 Comparisons using Control Sites
Appendix H 2 Regression-to-the-mean
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Appendix H 2.1 A Worked Example of Correction for Regression-to-the-mean (from Ogden 1996, p 458)
Tables
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Table 3.1: An example of threshold numbers used to identify sites for investigation
Table 4.1: An illustrative checklist of possible contributing factors, for use during site inspections
Table 4.2: Some possible contributing factors for different type of crashes
Table 4.3: Example Safe System treatments for various crash types
Table 4.4: Countermeasures for crashes at intersections and major driveways
Table 4.5: Countermeasures for non-intersection collisions
Table 4.6: Countermeasures for pedestrian/vehicle crashes
Table 4.7: Countermeasures for railway level crossing crashes
Table 5.1: Crash cost components for Australia and New Zealand
Table 5.2: Human capital average crash cost estimates for Australia at June 2013 prices (A$)
Table 5.3: Willingness to pay average crash cost estimates for Australia and New Zealand June 2013 prices (A$)
Table 5.4: Example crash costs by crash type (A$)
Table 5.5: Treatment life examples
Table 5.6: Illustrating discount factors for different discount rates
Table 5.7: Decision criteria for economic evaluation
Table 6.1: A guide to statistical tests
Table 6.2: Summary of treatments which may result in crash risk migration
Table B 1: Territory and Municipal Services Directorate, Australian Capital Territory
Table D 1: Crash data (example 1A)
Table D 2: Crash data (example 1B)
Table D 3: Abridged factor matrix
Table D 4: Crash data for practical example 6
Table D 5: Abridged factor matrix
Table E 1: Case study crashes at intersections
Table E 2: Case study crashes between intersections
Table E 3: Case study – factor matrix
Table E 4: Implementation costs for the case study options (A$)
Table E 5: Annual crash reduction savings for the case study options (A$)
Table E 6: Economic appraisal of case study options (A$)
Table F 1: Crash Modification Factors of Various Countermeasures for Intersection Crashes
Table F 2: Crash Modification Factors of Various Countermeasures for Non-intersection Crashes
Figures
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Figure 1.1: The steps in treating crash locations
Figure 2.1: Standard accident-type codes for definitions for coding accidents (DCAs) in Australia
Figure 2.2: Standard vehicular movement codes (VMCs) used in New Zealand
Figure 3.1: Example crash sites along a route
Figure 4.1: Example crash frequency histogram based on DCA code sub-groups
Figure 4.2: Example collision diagram
Figure 4.3: A report summary from a crash location investigation
Figure 4.4: Austroads Road Safety Engineering Toolkit – indicative screen example
Figure 4.5: Audio-tactile edgelines as a remedial treatment for run-off-road crashes
Figure A 1: Vegetation obstructing driver or rider’s view of potential conflict
Figure A 2: Poorly designed sign
Figure A 3: Example of a lane designation direction sign
Figure A 4: Example of sign installed incorrectly
Figure A 5: Example of an intersection where layout and priority are confusing
Figure B 1: Transport for NSW
Figure B 2: VicRoads
Figure B 3: Department of Transport and Main Roads Queensland
Figure B 4: Main Roads Western Australia
Figure B 5: Department of Planning, Transport and Infrastructure, South Australia (Pre 2013)
Figure B 6: Department of Planning, Transport and Infrastructure, South Australia (from January 2013)
Figure B 7: Department of State Growth, Tasmania – applies Victorian codes
Figure B 8: Department of Transport, Northern Territory
Figure D 1: T-intersection (example 1A)
Figure D 2: Collision diagram (example 1A)
Figure D 3: T-intersection (example 1B)
Figure D 4: Collision diagram (example 1B)
Figure D 5: Oxley Highway split in four sections
Figure D 6: Collision diagram
Figure D 7: Movement category pie chart
Figure D 8: Crash distributions – year, month, day and time
Figure D 9: Example of a roundabout installed within a local street
Figure D 10: Interchange used in practical example 5
Figure D 11: Looking south from where right turners wait to turn
Figure D 12: Collision diagram for practical example 6
Figure D 13: Intersection used in practical example 6
Figure D 14: Example of a recent traffic signal installation
Figure D 15: Looking north to the reconstructed bridge and curve
Figure E 1: Case study site plan (not to scale)
Figure E 2: Case study route plan showing road section and intersection numbers
Figure E 3: Case study collision diagram
Figure E 4: Vegetation obstructing signal on the southbound approach curve
Figure E 5: Inadequate lane width for southbound traffic on the south curve
Figure E 6: Lower cost case study treatment option (drawing not to scale)
Figure E 7: Higher cost case study treatment option (drawing not to scale)
Figure G 1: 1–8 occurrences per year
Figure G 2: 1–8 occurrences per year
Figure G 3: 8–30 occurrences per year (95% confidence level)
Figure G 4: 8–30 occurrences per year (95% confidence level)
Figure H 1: Comparison of crash data at treated and control sites
Appendix E 5 Summarising the Factors Identified from the Crash Listings, Factor Matrix and Collision Diagram
In this section
Appendix E 5.1 Intersections
Appendix E 5.2 Road Sections
Appendix E 5.3 Summary of Factors
Previous
Appendix E 4 Drawing a Collision Diagram and Identifying Clusters of Crash types at Locations
Next
Appendix E 5.1 Intersections
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