NCHRP Web-Only Document 427 Roadside Encroachment Database and Analysis

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COOPERATIVE RESEARCH PROGRAMS

CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 427

Monique R. Evans, Director, Cooperative Research Programs

Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program

Roberto Barcena, Senior Program Officer

Anthony Avery, Senior Program Assistant

Natalie Barnes, Director of Publications

Heather DiAngelis, Associate Director of Publications

Jennifer Correro, Assistant Editor

NCHRP PROJECT 17-88 PANEL
Field of Traffic – Area of Safety

Brian D. Burk, Travis County, Austin, TX

James L. Gattis, University of Arkansas, Fayetteville, Springfield, MO

Reza Ray Jafari, Road Safety and Transportation Solutions, Inc., Raleigh, NC

Chris Lindsey, Texas Department of Transportation, Austin, TX

James A. Mills, No Organization, Tallahassee, FL

Kelly K. Hardy, AASHTO Liaison

ACKNOWLEDGEMENTS

The research on which this report is based was conducted under the National Cooperative Highway Research Program (NCHRP) Project 17-88.

The research team would like to thank the many contacts within the Washington State, Iowa, and Tennessee Departments of Transportation who provided available crash, maintenance, and inventory data for this project. The research team would also like to acknowledge the efforts of Bucknell University research students that aided with the data collection as part of this project: Logan McGinn, Anthony Maceo, Charlie Buckwalter, Connor Rogan, and Ronan O’Driscoll.

Table of Contents

1. Introduction

1.1 Research Problem Statement

1.2 Objectives and Scope

2. Synthesis of Existing and Potential Encroachment Datasets and Collection Methods

2.1 Introduction

2.2 Approach

2.3 Encroachment Data Collection Methods

2.4 Existing Methods for Encroachment Data Collection

2.4.1 Field Collection Approach

2.4.2 ROR State Crash Data Approach

2.4.3 In-Depth Crash Study Approach

2.5 Potential Methods for Encroachment Data Collection

2.5.1 Naturalistic Driving Study (NDS) Methods

2.5.2 Event Data Recorder (EDR) Data

2.5.3 Google Street View Based Methods

2.5.4 Orthoimagery-Based Methods

2.5.5 Stationary Video Cameras

2.5.6 Infrastructure-Based Instrumentation

2.5.7 Vehicle-Based Methods

2.6 Available Encroachment Data Sources

2.6.1 Passenger Car Encroachment Data

2.6.2 Large Truck Encroachment Data

2.6.3 Motorcycle Encroachment Data

2.7 Summary

3. Development of the Encroachment Database

3.1 Background

3.2 Development of the NCHRP 17-88 Database

3.2.1 Approach

3.2.2 Data Element Needs

3.2.3 Data Sources

3.2.4 Summary of Data Availability

3.2.5 Data Element Catalog

3.2.6 Database Format

3.2.7 Database Size

3.3 Selection of Representative Segments from Available State Agency Partner Data

3.3.1 Objective and Approach

3.3.2 Determination of Range of Roadway, Roadside, and Traffic Characteristics

3.3.3 Evaluation of Potential Route Selection Schemes

3.3.4 Use Selection Scheme to Select Roadway Segments

3.3.5 Selection Results

3.3.6 Iowa State Representative Routes and Data

3.3.7 Washington State Representative Routes and Data

3.3.8 Tennessee State Representative Routes and Data

4. Characterizing the Nature and Frequency of Roadside Encroachments

4.1 State Data-Derived Encroachment Crash Rates and Influence of Roadway Characteristics

4.1.1 Road Segment Data

4.1.2 Reported and Unreported Crash Data

4.1.3 Methods

4.1.4 Road Segment Data Processing and Crash Merging

4.1.5 LOS Background and LOS Estimation

4.1.6 Roadway Characteristics and Model Development

4.1.7 Results

4.2 Discussion

4.3 Encroachment Modification Factors

4.3.1 Introduction

4.3.2 Methods

4.3.3 Results

4.3.4 Discussion and Future Work

5. Detailed Encroachment Characteristics

5.1 Characterization of Encroachments in the U.S. by Vehicle Type

5.1.1 Introduction

5.1.2 Methods

5.1.3 Results

5.1.4 Discussion

5.1.5 Conclusions

6. Findings and Recommendations

6.1 Findings

6.1.1 Review of Existing Encroachment Studies and Methods

6.1.2 Potential Encroachment Data Collection Methods and Selected Collection Method

6.1.3 NCHRP 17-88 Encroachment Database and Comparison to Existing Encroachment Data

6.1.4 Encroachment Frequency and Influence of Roadway Characteristics

6.1.5 Encroachment Characteristics

6.1.6 Vehicle Types and Encroachments

6.1.7 Unreported Crashes

6.2 Recommendations

6.2.1 Future Data Collection Efforts

6.2.2 MASH Impact Conditions

6.2.3 Motorcycles

6.2.4 EMFs

7. References

Appendix A: Literature Review Supplementary Material

Early Experiments for Improved Encroachment Data Collection

Data Collection Forms from Hutchinson and Kennedy Study and Cooper Study

Appendix B: Details of State Roadway Segment Selection

Appendix C: Coding and Analytical User’s Manual

List of Figures

Figure 1. Comparison of observed and estimated encroachment frequency for varying traffic volumes (Figure 3; Miaou 1997)

Figure 2. The SHRP 2 dataset contains 3,300 vehicles instrumented with multiple video views and lane-tracking sensors ideal for capturing roadside encroachments. Encroachment data (i.e., velocity and distance over the lane line) were recorded at 100 Hz.

Figure 3. EDR data downloaded from vehicles in ROR crashes can provide direct measurements of velocity at each off-road trajectory point along with attempted driver recovery actions (i.e., braking and steering inputs)

Figure 4. Three categories of encroachment severities

Figure 5. Distribution of encroachment-related crashes for divided roadways by land use and traffic volume

Figure 6. Distribution of encroachment-related crashes for undivided roadways by land use and traffic volume

Figure 7. Definitions of the distance to lane boundary (DTLB) variables

Figure 8. SHRP 2 lane tracking could lose lane position for larger lateral encroachments

Figure 9. The EMF by the number of lanes as computed for RSAPv3 and from SHRP 2

Figure 10. EMF by vertical grade

Figure 11. EMF by lane width for divided roadways

Figure 12. EMF by lane width for undivided roadways

Figure 13. EMFs by speed limit for divided and undivided roadways in SHRP 2

Figure 14. EMFs based on the radius of curvature for SHRP 2 roadways

Figure 15. The departure angle and the impact angles are measured relative to the roadway

Figure 16. The distribution of departure angles in the NCHRP 17-88 database by vehicle type

Figure 17. The distribution of impact angles in the NCHRP 17-88 database by vehicle type

Figure 18. Percent of crashes involving a rollover by vehicle type

Figure 19. Motorcyclist state prior to each impact event. The curves represent the transition of individual riders between states120

Figure 20. Distribution of objects struck during first event by vehicle type for cases in NCHRP 17-88

Figure 21. Distribution of posted speed for cases in NCHRP 17-88 by vehicle type

Figure 22. Distribution of number of lanes in the direction of travel for cases in NCHRP 17-88 by vehicle type

Figure 23. Distribution of roadway alignments by vehicle type for crashes in NCHRP 17-88

Figure 24. Distribution of roadway curvature radius by vehicle type in NCHRP 17-88

Figure 25. Distribution of AIS injury reports by vehicle type in NCHRP 17-88

Figure 26. Distribution of KABCO injury designations by vehicle type in NCHRP 17-88

Figure A-1. Form used in the field collection of median encroachment data (Hutchinson and Kennedy 1966)

Figure A-2. Encroachment shorthand graphical examples and zone coding convention (Hutchinson and Kennedy 1966)

Figure A-3. Roadside inventory data collection form used in the Cooper study (De Leuw Cather 1978)

Figure A-4. Encroachment data collection form used in the Cooper study – Page 1 (De Leuw Cather 1978)

Figure A-5. Encroachment data collection form used in the Cooper study – Page 2 (De Leuw Cather 1978)

Figure A-6. Encroachment frequency model for two-lane rural roads developed by Miaou (2001) using Washington State data

List of Tables

Table 1. Summary of Encroachment Data Collection Methods

Table 2. Summary of Hutchinson and Kennedy Methodology Variations by Investigation Purpose (Hutchinson 1962; Hutchinson and Kennedy 1966)

Table 3. Summary of NCHRP 17-11, FHWA Rollover Study, and NCHRP 17-22 Sampling Criteria (Mak et al. 2010)

Table 4. Summary of Supplemental Data Elements Collected/Determined Under NCHRP 17-22 (Mak et al. 2010)

Table 5. NCHRP 17-43 Supplemental Data Elements Not Included in NCHRP 17-22 (Gabler et al. 2012)

Table 6. Summary of RISER Detailed Database Sampling Criteria (Naing and Hill 2004)

Table 7. Summary of Encroachment Data and Reported Rates from Previously Published Studies

Table 8. Summary of Primary Encroachment Characteristics from Previously Published Studies

Table 9. Encroachment Characteristics by Vehicle Type Using Available Hutchinson and Kennedy (1966) Data

Table 10. Strengths and Limitations of Existing Roadside Encroachment Data Collection Methods

Table 11. Strengths and Limitations of Potential Roadside Encroachment Data Collection Methods

Table 12. Combined Data Elements from Hutchinson and Kennedy (H&K), Cooper, and the RDG Runout Table

Table 13. Data Needs for an Update to MASH Crash Test Conditions

Table 14. Additional Research Data Elements

Table 15. Combined Set of NCHRP 17-88 Data Needs

Table 16. Data Sources for the NCHRP 17-88 Encroachment Database

Table 17. High-level Summary of Data Needed and Potential Data Sources

Table 18. Summary of Police-reported Crash Data Needed

Table 19. Summary of Roadway and Roadside Inventory Data Needed

Table 20. Summary of Missing Inventory Data Elements from Washington and Iowa

Table 21. Summary of Maintenance Data Needed

Table 22. Case Table: Data Element Summary and Data Source Mapping

Table 23. Roadway Description Table: Data Element Summary and Data Source Mapping

Table 24. Roadside Encroachment Conditions Table: Data Element Summary and Data Source Mapping

Table 25. Vehicle Event Table: Data Element Summary and Data Source Mapping

Table 26. Encroachment Trajectory Table: Data Element Summary and Data Source Mapping

Table 27. Estimated Encroachment Database Size

Table 28. Roadway Characteristic Categories Based on Relevant RDG Table

Table 29. Roadway Characteristic Categories Based on RSAP Base Encroachment and Encroachment Adjustment Factors

Table 30. Roadway Types Considered in the HSM Predictive Methodology

Table 31. Potential Additional Roadway Characteristics to Consider in the Roadway Segment Selection Process

Table 32. Composite List of Roadway, Traffic, and Roadside Characteristics and Availability

Table 33. Roadway, Traffic, and Roadside Characteristics Used in the Roadway Selection Process

Table 34. Summary Results of State Agency Representative Route Selection

Table 35. Summary Characteristics of Selected Routes by Route Type and Subtype

Table 36. Summary Characteristics of Selected Iowa State Routes

Table 37. Comparison of Crash Characteristics for Selected IA Routes and All Similarly Classified Routes in the State

Table 38. Summary Characteristics of Selected Washington State Routes

Table 39. Comparison of Crash Characteristics for Selected WA Routes and All Similarly Classified Routes in the State

Table 40. Summary Characteristics of Selected Tennessee State Routes

Table 41. Comparison of Crash Characteristics for Selected TN Routes and All Similarly Classified Routes in the State

Table 42. Summary of Selected Washington State Roadway Segments and Traffic Exposure by Roadway Type

Table 43. Summary of Washington Roadway Segments for Selected Routes

Table 44. Summary of Washington State Crashes from 2012 through 2018 by Route Designation and Encroachment Type

Table 45. Excerpt of Freeway Generalized Service Volume by Area Type, Number of Lanes, and Truck Percent (Adapted from Margiotta and Washburn 2017)

Table 46. Roadway Types and Required Input Data

Table 47. Summary of Roadway Characteristics

Table 48. Mean Encroachment Rate (per MVMT) by Land Use and Roadway Segment Configuration

Table 49. Washington State Total and Unreported Encroachment Rate (per MVMT) by Roadway Type

Table 50. Washington State Unreported and Reported Impacts by Roadside Hardware Type

Table 51. Final Negative Binomial Model Results Predicting Number of Encroachment-related Crashes

Table 52. RSAPv3 EMFs for Number of Lanes; for Divided Roads, the Number of Lanes was for the Direction of Travel

Table 53. Encroachment Rate for Two-lane Undivided Roads and Four-lane Divided Roads Computed for RSAPv3 and in SHRP 2

Table 54. EMF for Number of Lanes from RSAPv3 and Computed with SHRP 2 Data; for Divided Roads, Number of Lanes was for the Direction of Travel

Table 55. EMF by Vertical Grade

Table 56. EMF by Lane Width for Divided and Undivided Roadways

Table 57. EMFs by Speed Limit for Divided and Undivided Roadways

Table 58. MASH Longitudinal Barrier Test Conditions for Passenger Vehicles and Large Trucks in TL-3+ Crash Tests

Table 59. Global Testing Conditions Used for Motorcycle Barrier Crash Testing

Table 60. Summary of Roadside Encroachment and Crash Datasets for Motorcycles

Table 61. Data Availability

Table 62. Distribution of Passenger Vehicle, Light Truck, and Motorcycle Impact and Departure Angles from NCHRP 17-88 Database by Vehicle Type

Table 63. Distribution of Passenger Vehicle, Light Truck, and Motorcycle Impact and Departure Angles from NCHRP 17-88 Database by Vehicle Type

Table 64. Data Sources for the NCHRP 17-88 Encroachment Database

Table 65. Summary of NCHRP 17-88 Database Relative to Previously Available Encroachment Datasets