CHAPTER 1 INTRODUCTION 1
1.1 GENERAL INTRODUCTION 1
1.2 OBJECTIVES 3
1.3 BOOK STRUCTURE 5
CHAPTER 2 LITERATURE REVIEW 7
2.1 EVALUATION CRITERIA AND PREDICTIVE MODELS FOR ROAD SAFETY PERFORMANCE 7
2.1.1 Role of exposure in road safety analyses 8
2.1.2 Predictive models for crash occurrence 9
2.1.3 Predictive models for crash severity 11
2.1.4 Integrated models 13
2.2 METHODS OF ANALYSES 14
2.2.1 Maximum likelihood estimation 15
2.2.2 Full Bayesian method 15
2.3 RISK FACTORS 17
2.3.1 Speed and road safety 17
2.3.2 Geometric and operational factors and road safety 19
2.3.3 Weather conditions and road safety 20
2.4 CONCLUDING REMARKS 20
CHAPTER 3 MODELING FRAMEWORK 21
3.1 MODELING APPROACH 21
3.1.1 Crash frequency models 22
3.1.2 Crash severity models 29
3.1.3 Joint probability models 31
3.2 ESTIMATION METHOD 37
3.2.1 Maximum likelihood estimation method 37
3.2.2 Bayesian method 39
3.3 CONCLUDING REMARKS 49
CHAPTER 4 SAFETY ANALYSIS FOR SIGNALIZED INTERSECTIONS 50
4.1 INTRODUCTION 50
4.2 DATA 52
4.3 MODEL SPECIFICATION 57
4.3.1 Probability function for crash occurrence 57
4.3.2 Probability function for crash severity 59
4.3.3 Joint probability function 60
4.4 RESULTS 61
4.5 DISCUSSION 63
4.5.1 Quadrant 1:Significant factors affecting crash occurrence and crash severity 64
4.5.2 Quadrant 2:Significant factors affecting crash occurrence only 65
4.5.3 Quadrant 3:Significant factors affecting crash severity only 66
4.6 CONCLUDING REMARKS 66
CHAPTER 5 SAFETY ANALYSIS FOR ROAD SEGMENTS 68
5.1 INTRODUCTION 68
5.1.1 Road safetyon road segments 68
5.1.2 Role ofexposure and speed in road safety analysis 70
5.2 DATA 71
5.2.1 Crash database 72
5.2.2 Speed measurement 75
5.2.3 Traffic volume and exposure 77
5.2.4 Explanatory factors 78
5.2.5 Data summary 79
5.3 MODEL SPECIFICATION 82
5.3.1 Probability function for crash occurrence 82
5.3.2 Probability function for crash severity 83
5.3.3 Joint probability functions 84
5.4 RESULTS 85
5.5 DISCUSSION 89
5.5.1 Speed and road safety 89
5.5.2 Effects of explanatory factors 92
5.6 CONCLUDING REMARKS 93
CHAPTER 6 CONCLUSIONS 95
6.1 GENERAL CONCLUSIONS 95
6.2 RECOMMENDATIONS FOR FUTURE RESEARCH 97
6.2.1 Alternative models in an integrated modeling framework 97
6.2.2 Bayesian updating function with prior information 98
6.2.3 Disaggregated safety analysis 99
APPENDIX A MOVING OBSERVER METHOD FOR SPEED DISTRIBUTION ESTIMATION 100
A.1 INTRODUCTION 100
A.2 MODEL DEVELOPMENT 102
A.3 MODEL CALIBRATION 104
A.4 MODEL VALIDATION 107
A.5 CONCLUDING REMARKS 108
APPENDIX B GPS PROBE METHOD FOR SPEED DISTRIBUTION ESTIMATION 109
B.1 INTRODUCTION 109
B.2 DATA 111
B.3 METHODOLOGY 112
B.3.1 Models for average travel speed 112
B.3.2 Models for speed dispersion 114
B.3.3 Full Bayesian method 114
B.4 RESULTS 115
B.4.1 Average travel speed 115
B.4.2 Speed dispersion 122
B.5 DISCUSSION 123
B.5.1 Average travel speed 123
B.5.2 Speed dispersion 125
B.6 CONCLUDING REMARKS 125
REFERENCES 126