1. I-10 Phoenix Corridor Safety Study I-10 Phoenix Corridor Safety Study 35 th Avenue to Sky Harbor Boulevard Safety Performance Evaluation Results Jim Schoen, PE Jim Bonneson, PhD, PE Jake Kononov 1 Workshop 2 September 23, 2014

2. I-10 Phoenix Corridor Safety Study Agenda 8:30 - 10:00 – Executive Summary Safety Performance Evaluation of the I-10 Study Section 10:15 - Noon – Development and application of Phoenix urban freeway crash prediction model on the I-10 study section 1:00 – 2:30 – Crash diagnostics 2:30 – 4:00 – Level of Service of Safety 2

3. I-10 Phoenix Corridor Safety Study Welcome and Introductions ADOT Project Management Team – Mark Hoffman – ADOT MPD – Project Manager – Maysa Hanna – ADOT State Traffic Engineer – Mark Poppe – Phoenix Regional Traffic Engineer – Richard Weeks – ADOT Traffic Safety – Kohinoor Kar – ADOT Traffic Safety – Tony Staffaroni – ADOT Communications ADOT Core Team – 17 members ADOT Project Team – 26 members Study Consultant Team – Kittelson & Associates – Lee Engineering – Works Consulting – Jake Kononov 3

4. I-10 Phoenix Corridor Safety Study Goals for Today’s Workshop Purpose of the workshop… – Present the results of the evaluation of safety performance on the I- 10 study section (Task 3) Describe the process to develop a Phoenix urban freeway crash prediction model Describe the safety performance of the study section relative to other Phoenix urban freeway sections – Present the process for diagnosing crash causes or crash patterns that can be evaluated further for potential countermeasures Desired outcomes from today’s workshop… – Understanding of the tools developed for the evaluation of safety performance on Phoenix freeways – Feedback on the priority study section segments – Understanding of the next steps in the safety evaluation process 4

5. I-10 Phoenix Corridor Safety Study Executive Summary Safety Performance Evaluation of the I-10 Study Section – Scope Refresher Goals Tasks – Evaluation Methodology – Evaluation Results Crash Summary Phoenix Urban Freeway Crash Prediction Model(s) I-10 Study Section Performance – Priorities for improvement Key Outcomes – Next Steps – Discussion 5

6. I-10 Phoenix Corridor Safety Study Study Goals 1.Quantify safety performance on the study section using the advanced analytical methods described in the Highway Safety Manual 2.Identify and prioritize potential opportunities to reduce crashes through the implementation of cost effective countermeasures 6

7. I-10 Phoenix Corridor Safety Study Study Goals 3.Expand ADOT’s safety planning and management capabilities by providing – analytical tools calibrated for Phoenix freeways – training in data gathering and application of the HSM methods 7

8. I-10 Phoenix Corridor Safety Study Study Tasks Task 1: Technical Memorandum 1 – Refine Work Plan Task 2: Project Team Workshop 1 Task 3: Identify Relative Safety Performance of Freeway Segments Task 4: Project Team Workshop 2 Task 5: Diagnose Crash Trends, Identify Countermeasures, Develop Benefits and Cost Estimates Task 6: Develop Safety Evaluation Framework Task 7: Draft Final Report Task 8: Final Report 8

9. I-10 Phoenix Corridor Safety Study Study Section 9

10. I-10 Phoenix Corridor Safety Study Safety Performance Evaluation Methodology Highway Safety Manual Methodology – Assess safety performance relative to typical Phoenix urban freeways. Is there a potential safety issue on segment? Compare expected long term crash frequencies Crash prediction models – Determine the potential for safety improvement on a segment – Prioritize roadway segments for detailed analysis Performance measures – Diagnosis of crash causes – Countermeasure evaluation 10

11. I-10 Phoenix Corridor Safety Study Safety Performance Evaluation Methodology Freeway Crash Prediction Models – Developed by research project NCHRP 17-45 – N p = N SPF x CMF 1 x CMF 2... x CMF n x C Predicts crashes, by type and severity, based on roadway geometry (# lanes, lane width, curvature, etc) and features (barrier, clear zone, rumble strips) and traffic conditions (AADT, level of congestion) – Calibrated to local conditions Climate, driver behavior, driver population, speed limit, enforcement, driving laws, crash reporting practices, and other unknown factors 11

12. I-10 Phoenix Corridor Safety Study Safety Performance Evaluation Methodology Crash Prediction Model Calibration – 38 freeway segments I-10, I-17, SR 101, SR 202, US 60 6-12 lanes HOV lanes (all) Varying horizontal curvature Weaving sections (with/without) Ramp metering (all) 129,000 – 240,000 ADT 12

13. I-10 Phoenix Corridor Safety Study Evaluation Results Crash Summary 13 Urban Freeways Fatal (K) and Injury (A,B,C)Total (K,A,B,C,PDO) Crash Count, cr Crash Rate, cr/mvm Crash Count, cr Crash Rate, cr/mvm Phoenix Calibration Segments (3-yrs)11670.4736581.47 Phoenix I-10 Study Section (3-yrs)14270.9049003.10 Maine1130.213400.63 Utah10150.3431031.03 Illinois46980.4615,1561.48 Minnesota20540.3077321.12 Oregonnot available 36940.64 Dallas-Ft. Worthnot available 20,5300.75 Washington, Maine, California combined 51120.2416,2050.76

14. I-10 Phoenix Corridor Safety Study Evaluation Results Distribution of Crash Severity 14 PDOCBAK Phoenix Calibration Segments 0.680.170.130.020.002 Phoenix I-10 Study Section 0.710.160.110.010.002 PDO: property damage only C: possible injury B: non-incapacitating injury A: incapacitating injury K: fatal

15. I-10 Phoenix Corridor Safety Study Evaluation Results Phoenix Urban Freeway Crash Prediction Models – 8 models calibrated – Predict crashes by type and severity 15 Urban Freeway SegmentsUrban Freeway Speed-change Lanes  Multiple vehicle crashes – FI  Multiple vehicle crashes – PDO  Single vehicle crashes – FI  Single vehicle crashes - PDO  Multiple vehicle crashes – FI  Multiple vehicle crashes – PDO  Single vehicle crashes – FI  Single vehicle crashes - PDO

16. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance Performance Measures – Probability of Specific Crash Type Exceeding Threshold Proportion – Excess Proportion of Specific Crash Type – Expected Average Crash Frequency with EB Adjustment – Equivalent PDO Average Crash Frequency with EB Adjustment – Excess Expected Average Crash Frequency with EB Adjustment – Level of Service of Safety (LOSS) with EB Adjustment 16

17. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance 17

18. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance 18

19. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance 19

20. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance 20

21. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance 21

22. I-10 Phoenix Corridor Safety Study I-10 Study Section Performance Many of study section segments are problematic relative to typical urban Phoenix freeways – Confirms the need for this study and for safety improvement Majority of study section has good potential for crash reduction (LOSS) Priority segments – 35 th Ave – 19 th Ave to SR 51 – Sky Harbor Blvd 22

23. I-10 Phoenix Corridor Safety Study Key Outcomes Data Availability and Quality – Roadway Geometry and Features Aerial based data collection method demonstrated; ADOT staff trained Potential RCID improvements – Traffic Data TDMS data suitable FMS historical data provides congestion information – Crash Data Crash location reporting significantly improved with TraCs 23

24. I-10 Phoenix Corridor Safety Study Key Outcomes Analytical Tools Developed – Calibrated Phoenix urban freeway crash prediction model – Safety performance evaluation spreadsheet (ISATe) – Available for: Safety performance evaluation of other urban freeway sections Safety evaluation of freeway design alternatives Safety evaluation of design exceptions 24

25. I-10 Phoenix Corridor Safety Study Next Steps Crash Diagnosis – Priority segments Tunnel lighting Left-hand ramps – Section-wide contributing factors Speed Continuous access HOV lanes – Identify and evaluate potential countermeasures 25

26. I-10 Phoenix Corridor Safety Study Discussion 26

27. I-10 Phoenix Corridor Safety Study Break – 15 Minutes 27

28. I-10 Phoenix Corridor Safety Study Overview Overview of Evaluation Methodology Model Calibration Study Section Evaluation Process Network Screening Diagnosis (Task 5) 28

29. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Terms and Concepts Predictive Models Application of the Models for this Study Variation in Reported Crashes Among Jurisdictions 29

30. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Terms and Concepts – Segment Length of freeway between stated begin-milepost and end-milepost 30

31. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Terms and Concepts – Speed-change lane Portion of segment Located on roadbed served by the speed-change lane, between gore and taper points Region A 31

32. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Terms and Concepts – Basic segment Portion of segment. Excludes speed-change lane. 32 Basic Segments

33. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Terms and Concepts – Crash assignment Speed-change-related crash – Crashes occurring in speed-change lane (i.e., Region A) Basic-segment crash – Crashes not assigned to a speed-change lane 33

34. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Predictive Models – Freeway segment model Evaluates basic segment – Speed-change lane model Form – N p = C x N SPF x CMF 1 x CMF 2... x CMF n – with N spf = a × (AADT) b × L – Coefficients a and b by... Area type Number of lanes Crash type Severity 34

35. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology CMFs – Horizontal curve – Lane width – Paved shoulder width Inside Outside – Median width – Barrier Median Roadside 35 – High volume (congestion) – Lane change (ramp related) – Shoulder rumble strips – Outside clearance – Ramp entrance – Ramp exit

36. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Limitations – Freeways with 13 or more lanes SPF coefficients were adjusted to address 11, 12 ft – Continuous access HOV lanes Effect included in calibration factor – Ramp metering Effect included in calibration factor – Use of safety shoulders as travel lanes – Toll plazas – Reversible lanes 36

37. I-10 Phoenix Corridor Safety Study Overview of the Evaluation Methodology Verification – Comparison of crash rates Data for locations in last row used to calibrate models 37

38. I-10 Phoenix Corridor Safety Study Model Calibration Candidate Freeway Sections Segmentation Process Calibration Database Development Calibration Factors 38

39. I-10 Phoenix Corridor Safety Study Model Calibration Candidate Freeway Sections – Selection criteria Goal: 30 or more typical freeway segments in Phoenix metro area Avoid unusual conditions – Grade > 4% – Speed limit 70 mi/h – Shoulder used as travel lane – Reversible lanes – Work zone present for extended time period 39

40. I-10 Phoenix Corridor Safety Study Model Calibration Candidate Freeway Sections 40

41. I-10 Phoenix Corridor Safety Study Model Calibration Segmentation Process – Segmentation criteria Number-of-lanes change Lane width changes by 0.5 ft or more Shoulder width changes by 1 ft or more Clear zone width changes by 5 ft or more Median width changes by 10 ft or more Presence of ramp gore point – Aerial imagery used to evaluate and define segments 41

42. I-10 Phoenix Corridor Safety Study Model Calibration Segmentation Process – Original 40 segments SR 101: 9 segments US 60: 5 segments SR 202: 2 segments I-17: 4 segments I-10: 20 segments (9 of 20 on I-10 study section) 13.0 miles – Final 38 segments 2 segments ultimately excluded (considered outliers) 11.9 miles 42

43. I-10 Phoenix Corridor Safety Study Model Calibration Segmentation Process – Original segments Basic segments: 39 Entrance speed-change lanes: 7 Exit speed-change lanes: 17 – Final segments Basic segments: 37 Entrance speed-change lanes: 5 Exit speed-change lanes: 14 43

44. I-10 Phoenix Corridor Safety Study Model Calibration Calibration Database Development – Road geometry Aerial imagery Plans for tunnel – Traffic volume data Traffic Data Management System (TDMS) website AADT – 2013 most reliable – AADTs computed for segments between count stations Portion of AADT during hours where volume exceeds 1,000 veh/h – Computed from hour-of-day-by-month-of-year data (FMS) 44

45. I-10 Phoenix Corridor Safety Study Model Calibration Calibration Database Development 45

46. I-10 Phoenix Corridor Safety Study Model Calibration Calibration Database Development – Crash Data Electronic files from ADOT for 2011, 2012, 2013 – Clustering of crashes on “even-mile” mileposts for 2011 » Even-mile milepost examples: 143.00, 144.00, 145.00 » Indicates 1-mile precision for crash location – Data for all three years retained for calibration » Location bias should average out Crash Count – 3658 crashes/3 years – 13.0 miles; 40 segments – 1.47 crashes/mvm » Compare to range of 0.63 to 1.48 cr/mvm » Compare to 0.76 cr/mvm for Washington, Maine, Calif. 46

47. I-10 Phoenix Corridor Safety Study Model Calibration Calibration Factors – Basic segments – Speed-change lanes 47 Single-Vehicle PDO Single-Vehicle Fatal+Injury Multple-Veh. PDO Multiple-Veh. Fatal+Injury Reported Crashes3461351690782 Predicted Crashes3081431233479 Calibration Factor1.120.941.371.63 Entrance PDO Entrance Fatal+Injury Exit PDO Exit Fatal+Injury Reported Crashes67366823 Predicted Crashes29.315.931.814.5 Calibration Factor2.292.272.141.58

48. I-10 Phoenix Corridor Safety Study Study Section Evaluation Process Segmentation Process Study Section Database Development Safety Management Process 48

49. I-10 Phoenix Corridor Safety Study Study Section Evaluation Process Segmentation Process – 30 segments 7.6 miles – 9 segments (2.6 miles) also in calibration database – Composition Basic segments: 29 Entrance speed-change lanes: 12 Exit speed-change lanes: 17 49

50. I-10 Phoenix Corridor Safety Study Study Section Evaluation Process Study Section Database Development – Road geometry Same source and method as used for calibration data – Traffic volume data Same source and method as used for calibration data 50

51. I-10 Phoenix Corridor Safety Study Study Section Evaluation Process Study Section Database Development – Crash Data Electronic files from ADOT for 2012, 2013 – Crash location accuracy is reliable to 0.1 mile or less Crash Count – 3250 crashes/2 years – 7.6 miles – 30 segments – 3.1 crashes/mvm » Compare to range of 0.63 to 1.48 cr/mvm 51

52. I-10 Phoenix Corridor Safety Study Study Section Evaluation Process Safety Management Process – Network screening – Diagnosis – Countermeasure selection – Economic assessment – Prioritize projects – Safety effectiveness evaluation 52 Task 5 Task 3

53. I-10 Phoenix Corridor Safety Study Network Screening Objective – Identify sites with most potential for safety improvement Safety improvement measured by reduction in crash freq. – Cost-effectiveness of treatment is determined in Economic Assessment task Steps – Select performance measures – Select screening method – Evaluate results Outcome – List of sites with most potential for safety improvement 53

54. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Candidate measures Annual frequency of reported crashes Rate (in crashes/mvm) of reported crashes Prob. of a crash type proportion exceeding a threshold Excess proportion of crash type Expected average crash frequency (w/EB adj.) EPDO average crash frequency (w/EB adj.) Excess expected average crash frequency (w/EB adj.) Modified Level of Service of Safety (w/EB adj.) 54

55. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Selection considerations Ability to identify sites with high average crash freq. – These sites likely to have most potential for improvement Ability to identify sites with relatively high crash risk – These sites likely to be more amenable to treatment Minimizes influence of random variation in crash count – If no, then measure may be unreliable (esp. when few crashes) Minimizes regression-to-the-mean bias Does not need predictive model to compute measure – If no, some effort required to calibrate model and get input data Can evaluate overall site and specific crash types – If no, cannot describe overall site, so best use is in Diagnosis task 55

56. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Annual frequency of reported crashes (AFC) AFC = Count of crashes / years considered in count – Assessment Not a reliable indicator of improvement potential 56 ConsiderationMet Ability to identify sites with high average crash freq.Yes Ability to identify sites with high crash riskNo Minimizes influence of random variation in crash countNo Minimizes regression-to-the-mean biasNo Does not need predictive model to compute measureYes Can evaluate overall site and specific crash typesYes

57. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Rate (in crashes/mvm) of reported crashes (CR) CR = Count of crashes / million-vehicle-miles traveled – Assessment Not a direct indicator of improvement potential Not a reliable indicator of crash risk 57 ConsiderationMet Ability to identify sites with high average crash freq.No Ability to identify sites with high crash riskYes Minimizes influence of random variation in crash countNo Minimizes regression-to-the-mean biasNo Does not need predictive model to compute measureYes Can evaluate overall site and specific crash typesYes

58. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Prob. of a crash type proportion exceeding a threshold (P) P = based on proportion for subject site compared to the distribution of proportions for all sites – Assessment Not a direct indicator of improvement potential Useful in Diagnostic task 58 ConsiderationMet Ability to identify sites with high average crash freq.No Ability to identify sites with high crash riskNo Minimizes influence of random variation in crash countYes Minimizes regression-to-the-mean biasNot applicable Does not need predictive model to compute measureYes Can evaluate overall site and specific crash typesNo

59. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Excess proportion of crash type (EP) EP = proportion for subject site – proportion for reference sites – Assessment Not a direct indicator of improvement potential Useful in Diagnostic task 59 ConsiderationMet Ability to identify sites with high average crash freq.No Ability to identify sites with high crash riskNo Minimizes influence of random variation in crash countNo Minimizes regression-to-the-mean biasNot applicable Does not need predictive model to compute measureYes Can evaluate overall site and specific crash typesNo

60. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Expected average crash frequency (w/EB adj.) (EACF+EB) EACF+EB = model prediction + reported crash freq. – Assessment A direct indicator of improvement potential CMFs can be used to assess risk (of specific features) 60 ConsiderationMet Ability to identify sites with high average crash freq.Yes Ability to identify sites with high crash riskSome Minimizes influence of random variation in crash countYes Minimizes regression-to-the-mean biasYes Does not need predictive model to compute measureNo Can evaluate overall site and specific crash typesYes

61. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – EPDO average crash frequency (w/EB adj.) EPDO+EB = model prediction + reported crash freq. – Assessment Gives higher weight to severe crashes Can over-emphasize sites with a few serious crashes 61 ConsiderationMet Ability to identify sites with high average crash freq.Yes Ability to identify sites with high crash riskSome Minimizes influence of random variation in crash countYes Minimizes regression-to-the-mean biasYes Does not need predictive model to compute measureNo Can evaluate overall site and specific crash typesYes

62. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Excess expected average crash frequency (w/EB adj.) Excess+EB = expected - predicted – Assessment CMFs can be used to assess risk (of specific features) Excess is an indication of risk (of unspecified features) 62 ConsiderationMet Ability to identify sites with high average crash freq.No Ability to identify sites with high crash riskYes Minimizes influence of random variation in crash countYes Minimizes regression-to-the-mean biasYes Does not need predictive model to compute measureNo Can evaluate overall site and specific crash typesYes

63. I-10 Phoenix Corridor Safety Study Network Screening Select Performance Measures – Modified Level of Service of Safety (w/EB adj.) Z score = (expected – predicted)/standard deviation – Assessment CMFs and LOSS can be used to assess risk Z score = normalized degree of risk across all sites 63 ConsiderationMet Ability to identify sites with high average crash freq.No Ability to identify sites with high crash riskYes Minimizes influence of random variation in crash countYes Minimizes regression-to-the-mean biasYes Does not need predictive model to compute measureNo Can evaluate overall site and specific crash typesYes

64. I-10 Phoenix Corridor Safety Study Network Screening Select Screening Method – Options Rank Sliding window Peak searching – Choice Rank Rationale: works best with unequal segment lengths 64

65. I-10 Phoenix Corridor Safety Study Network Screening Evaluate Results – Sites with higher rank most likely to benefit from treatment – Process Rank sites by Z score, remove those with Z < 0.0 Rank sites by “combined” CMF, remove those CMF < 1.0 Combine the two lists – List contains higher risk sites likely to be amenable to treatment Rank remaining sites in order of expected average crash frequency – List includes sites with most potential for improvement and with sufficiently high risk as to be amenable to treatment 65

66. I-10 Phoenix Corridor Safety Study Diagnosis Objective – Identify causes of crashes and potential safety concerns Focus on list of sites identified in Network Screening task Undertaken on site-by-site basis Typically will find one cause, but may find many small causes Steps – Review crash statistics and crash reports – Assess field conditions – Evaluate elements associated with CMF > 1.0 – Identify likely crash causes Outcome – List of crash causes for each site with potential for improvement 66

67. I-10 Phoenix Corridor Safety Study Diagnosis Information for Diagnosis – Where to look for crash causes – Example site with given AADT 67

68. I-10 Phoenix Corridor Safety Study Diagnosis Information for Diagnosis – Where to look for crash causes – Example site with given AADT 68

69. I-10 Phoenix Corridor Safety Study Next Steps Task 5 – Diagnose safety problems – Identify and evaluate countermeasures – Quantify countermeasure benefits and costs Diagnosis Considerations – Influence of excessive speed – Influence of HOV ramps – Influence of tunnel presence – Influence of congestion 69

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78. I-10 Phoenix Corridor Safety Study Crash Diagnostics Prioritize Segments – 39 basic segments – 29 speed-change lanes 78

79. I-10 Phoenix Corridor Safety Study Diagnosis Information for Diagnosis – Where to look for crash causes – Example site with given AADT 79

80. I-10 Phoenix Corridor Safety Study Crash Diagnostics 80 ISATE – Evaluate CMFs ISATe_V06j_az1-I10-A_tunnel.xls – Review crash data for patterns Location Severity Type Time-of-day – Review crash reports Narrative – Field review