Diagnosis Process. Learning Outcomes. Roadway Safety Management Process Overview MODULE 9. DIAGNOSIS AND COUNTERMEASURE SELECTION

Transcription

1 Network Screening HSM Vol. 1 (Part B) Chapters 5 & 6 MODULE 9. DIAGNOSIS AND COUNTERMEASURE SELECTION Roadway Safety Management Process Overview Diagnosis and Countermeasure Selection Economic Appraisal and Prioritization Safety Effectiveness Evaluation Learning Outcomes Diagnosis process Crash and supporting data Field evaluation Contributing factors Countermeasure selection and application 9-3 Diagnosis Process STEP 1: Review safety data STEP 2: Assess supporting documentation STEP 3: Assess field conditions Desired Outcomes Understand site conditions Identify crash patterns Gain insight on countermeasure selection 9-4 Module 9 1

2 Safety Data Review Descriptive statistics Crash conditions Crash type Crash severity (KABCO) Environmental conditions Event sequence Contributing factors Crash locations Diagnosis and Countermeasure Selection N Golf Road <34,800> 1 st Avenue <17,500> 9-5 Google Earth 9-6 Sidewalk Diagnosis Tools Condition Diagrams Bank School Playground Example of Verified Field Review Signalized intersection Left turn lanes in all quadrants Permissive/protected phasing Pedestrian crossings and signal control Clearance interval not adequate for prevailing speeds Driveway Tree Light Pole Pothole Sidewalk Module 9 2

3 Collision Diagram Collision Diagram Example Site Crash Types Other Non-Collision; Other Object; Parked Car & Train Pedestrian & Bicyclist Animal Rear End and Same Direction Sideswipe Angle and Turning Fixed Object & Overturned Diagnosis Tools Other Supporting Documentation Land use maps Historic weather patterns Public comment records Roadway improvement plans Anecdotal information Head-On & Opposite Direction Sideswipe Crash Frequency over 5 years Module 9 3

4 Summary Safety Diagnosis Essentials Data - sufficient quantity and quality Field observations Diagnostic tools Knowledge Safety fundamentals Human factors Traffic and highway engineering Good judgment Network Screening Diagnosis and Countermeasure Selection Economic Appraisal and Prioritization Safety Effectiveness Evaluation Countermeasures (Chapter 6) Identify contributing factors Select potential countermeasures or treatments Apply countermeasures Identify Contributing Factors Haddon Matrix (Rear End Crash) Roadway Period Human Factors Vehicle Factors Roadway Factors Vehicle Human Before Distraction Impairment Poor Driving Bald Tires Poor Brakes Poor Traction Steep Grade Poor Signage During Not Belted Age Vulnerability Airbag Bumper Height Headrest Poor Traction Steep Grade After Age Gender Occupant Egress EMT Time/Quality Module 9 4

5 Contributing Crash Factors HSM Categories Roadway Segments Signalized Intersections Unsignalized Intersections Highway-Rail Grade Crossings Pedestrians Bicyclists Example Possible Contributing Factors - Signalized Intersections 9-17 (See p. 6-5 and 6-6 of the HSM ) 9-18 Contributing Factors for Severe Crash Types Angle and turning (left) Misjudging speed of opposing traffic Visibility of signals Inadequate signal timing Rear end (east approach) Inappropriate or excessive approach speeds Unexpected stops (driveways/access) 9-19 Select Potential Countermeasures Identify potential contributing factors Relate contributing factors to treatable actions Identify and list potential countermeasures Conduct cost benefit analysis Determine and recommend preferred treatment(s) 9-20 Module 9 5

6 Diagnosis: Basic Findings at One Candidate Intersection Traffic Control Two way Stop Number Approach Legs Major/ Min or AADT 4 22,100/ 1,650 Urban/ Rural Urban What are the likely contributing crash factors? 3 Year Crash Total Step 1. Diagnosis: Basic Findings (Cont.) Predominant Crash Types Crash Severity Fatal Injury PDO 35 Angle, Head on 6% 65% 29% What are the likely contributing crash factors? * Crash Modification Factor (CMF) A value which quantifies the change in crash frequency at a site resulting implementing a specific treatment or countermeasure CMF versus Crash Reduction Factor (CRF) How would a 12% reduction in crashes due to implementing a countermeasure be portrayed as a CMF and as a CRF? CMFs Located in HSM Vol. 3 (Part D) CMF =.88 CRF = 12% reduction or -12% 9-23* 9-24* Module 9 6

7 Countermeasure Evaluation HSM SPFs and CMFs Establish Base Condition: Model Intersection or Segment using applicable HSM SPFs Apply CMFs to model the base condition Apply local calibration factor Calculate crashes by type and severity Countermeasure Evaluation HSM SPFs and CMFs Estimate Countermeasure Effectiveness: Obtain Applicable CMFs for the various candidate treatments Apply CMFs to the Base Condition Model Compare predicted crash reductions for each treatment 9-25* 9-26* Intersection 2 Information and Partial Data Site Information Highway Intersection Intersection 2 1st Ave and Golf Rd Jurisdiction Anywhere, USA Analysis Year 2005 Input Data Intersection Type 4SG AADT major (veh/day) 34,800 AADT minor (veh/day) 17,500 Intersection Lighting (present/not present) present Calibration factor (C i ) 0.88 Left Turn Lanes Worksheet 2B CMFs for Base Condition (1) (2) (3) (4) (5) (6) Left Turn Right Signal Right Turn Turn on Phasing Lanes Red Lighting CMF 1i CMF 2i CMF 3i CMF 4i CMF 5i CMF 6i Equation Equation and Equation Red Light Cameras Combined CMF (1) X (2) x (3) X (4)x (5) Module 9 7

8 Worksheet 2D - Multiple-Vehicle Collisions by Collision Type (1) (2) (3) (4) (5) (6) Crashes per year by severity level Fatal and injury Property damage only Total Proportion of Proportion of collision type collision type Collision Type Based on Final (N bimv ) FI (2)x(3) TOT Based on Final (N bimv ) PDO (4)x(5) TOT Final N bimv (3)+(5) Total Rear end collision Head on collision Angle collision Sideswipe Other multiplevehicle collision Worksheet 2F - Single-Vehicle Collisions by Collision Type (1) (2) (3) (4) (5) (6) Collision Type Crashes per year by severity level Fatal and injury Property damage only Total Proportion of collision type Final (N bisv ) FI Proportion of collision type Final Final (N bisv ) PDO N bisv From From (2)x(3) TOT 13 (4)x(5) TOT (3)+(5) Total Collision with parked vehicle Collision with animal Collision with fixed object Collision with other object Other single vehicle collision Single vehicle non collision Worksheet 2H Vehicle-Pedestrian Collision CMFs (1) (2) (3) Bus Stops Schools Alcohol Sales Establishments CMF 1p CMF 2p CMF 3p Combined CMF (1)x(2)x (3) Worksheet 2I Vehicle-Pedestrian Collisions (1) (2) (3) (4) (5) (6) (7) Coefficients ( for 4 leg signalized Initial Combined Calibration Final intersections) N pedbase CMFs Factor N pedi Crash severity level a b c d e k Eqn (3)x(5)x (6) Total Fatal and Injury Property Damage Only Module 9 8

9 Worksheet 2J Vehicle-Bicycle Collisions (1) (2) (3) (4) (5) (6) (7) Calibration Final Final Final Crash f N severity bimv N bisv N bikei bi Factor Final N bikei level (4)x(5)x(6) Total Fatal and Injury Property Damage Only Worksheet 2K Crash Summary (Base Condition) Crash Severity (1) (2) (3) (4) Crashes per year by severity level Collision Type Fatal and injury Property damage only Total MULTIPLE VEHICLE COLLISIONS Rear end collision Head on collision Angle collision Sideswipe Other multiple vehicle collision Subtotal SINGLE VEHICLE COLLISIONS Collision with parked vehicle Collision with animal Collision with fix object Collision with other object Other single vehicle collision Single vehicle non collision Collision with pedestrian Collision with bicycle Subtotal Total Countermeasure Evaluation Countermeasure Roundabout construction Protected left-turn signal Red light running camera installation Interchange construction CMF Total crashes Fatal and Injury crashes Total crashes 0.92 Fatal and Injury crashes Total crashes Fatal and Injury crashes Total crashes Fatal and Injury crashes 9-35 Predicted Crash Frequency Intersection Without Countermeasures Calendar Year Major Road AADT Minor Road AADT N Pred(TOT) N Pred(FI) ,800 17, ,496 17, ,206 18, ,930 18, ,669 18, ,422 19, ,190 19, ,974 20, ,774 20, ,589 20, : : : : : : : : : : ,799 31, Total Note: The predicted crash frequency number previously reviewed demonstrated calculations for Year Module 9 9

10 Predicted Crash Frequency Total, Fatal and Injury with Countermeasures Countermeasure 1: Roundabout Total Crashes Fatal and Injury Crashes Calendar Year N E,Y(TOT) CMF1 (TOT) N Ev,Y(TOT) N E,Y(FI) CMF1 (FI) N Ev,Y(FI) : : : : : : : : : : : : : : Total Predicted Crash Reduction Total, Fatal and Injury, and PDO Crashes with Countermeasures Countermeasure 1: Roundabout Calendar Year N Ev, y(tot) N Ev, y(fi) N Ev, y(pdo) : : : : : : : : Total Total Predicted Crash Reduction for 30 Year Service Life Countermeasure Fatal & Injury Crashes PDO Crashes Total Crashes Roundabout Protected left turn signal Red light running camera Countermeasure Evaluation Protected left-turn signal produces small positive crash reduction Red-light camera would increase overall crashes Infrastructure solutions produce greater positive crash reductions but with greater investment Interchange Module 9 10

11 Network Screening Roadway Safety Management Process Overview Diagnosis and Countermeasure Selection Economic Appraisal and Prioritization Safety Effectiveness Evaluation Summary MODULE 9. DIAGNOSIS AND COUNTERMEASURE SELECTION Module 9 11