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Are They Sick? Evaluating Corridors from a Safety Health Perspective Bill Loudon and Bob Schulte, DKS Associates Prepared by IDAHO TRANSPORTATION DEPARTMENT.

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Presentation on theme: "Are They Sick? Evaluating Corridors from a Safety Health Perspective Bill Loudon and Bob Schulte, DKS Associates Prepared by IDAHO TRANSPORTATION DEPARTMENT."— Presentation transcript:

1 Are They Sick? Evaluating Corridors from a Safety Health Perspective Bill Loudon and Bob Schulte, DKS Associates Prepared by IDAHO TRANSPORTATION DEPARTMENT Prepared by IDAHO TRANSPORTATION DEPARTMENT 1 April 3, 2013 Highway Safety Corridor Analysis Project

2 Presentation Outline 1.Study Overview 2.Network Screening Method 3.Diagnosis of Safety Problems 4.Identification of Countermeasures 5.Evaluation of Potential Countermeasures 6.Summary of Benefits 2

3 1. Overview of Study 3

4 Study Background Origins of Study District 6 Corridor Health Assessment District 6 Safety Needs Pilot Study Statewide Application with District Orientation 4

5 Corridor Health Assessment 5

6 Corridor Health Scoring FactorWeightFactor Score Safety40%.35*(% of State VMT for Category with Fatal Accident Rate greater than or equal to the Segment) +.35*(% of State VMT for Category with Injury Accident Rate greater than or equal to the Segment) +.3*(% of State VMT for Category with Total Accident Rate greater than or equal to the Segment) Travel Time and Delay 30%1/LOS where LOS =.5 * (Link LOS for Average Peak Hour Conditions) +.2 * (Link LOS for Design Hour Volume) +.2 * (Int. LOS for Average Peak Hour Conditions) +.1 * (Int. LOS for Design Hour Volume) Where LOS = 1 for C or better, 2 for D, 3 for E and 5 for F Ride Quality 10%1/PC where PC= 1 for Good, 2 for Fair, 3 for Poor and 5 for Very Poor Pavement Condition Rating Points of Access 10%=1-(Number of Access Points per mile) / (Number Allowed by Guidance for the Roadway Type) Shoulder Width 10%Average of Width/Guidance Standard up to 1 6

7 District 6 Safety Needs Pilot Study 7

8 What is the Highway Safety Manual? Purpose Provide analytical tools and techniques for quantifying the safety effects of decisions made in planning, design, operations, and maintenance Objective Reduce the number and severity of crashes within the limits of available resources, science, technology, and legislatively mandated priorities 8

9 Highway Safety Corridor Analysis (HSCA) Project Objectives Introduce use of a data-driven analytical process: Identify the highest-priority locations for safety improvements Identify improvement options for reducing crashes and crash severity Evaluate and prioritize improvement options Implement projects to construct the high-priority improvements Evaluate the improvements 9

10 Significant Study Outcomes Application of: A District-wide and State-wide Safety Analysis Methodology The Highway Safety Manual Advanced use of GIS data to support planning and project prioritization Advanced use of ITD Digital Video Logs Advanced use of web-based tools – Google Earth Gap Analysis of the Process 10

11 2. Network Screening Method 11

12 First Stage Screening - Priority Safety Segments Safety Health Score =.35*(% of State VMT for Category with Fatal Crash Rate greater than or equal to the Segment) +.35*(% of State VMT for Category with Injury Crash Rate greater than or equal to the Segment) +.3*(% of State VMT for Category with Total Crash Rate greater than or equal to the Segment)

13 Safety Priority Rating High – Safety score worse than or equal to 70% of the other segments of the same “Corridors of Importance” category. Medium – Safety score better than 30% of the other segments but worse than 30%. Low – Safety score better than or equal to 70% of the other segments.

14 Priority Segments Based Safety Health Score 14

15 ITD Corridors of Significance Classifications Investment Corridor Analysis Planning System (ICAPS)

16 Sample of Priority Segments All Routes

17 Sample of Priority Segments Interstate and Statewide Priority

18 Sample Priority Safety Segment Information 18

19 Second Stage Screening – Priority Safety Improvement Locations

20 Selection Criteria for Safety Improvement Locations Safety health score Minimum of three crashes over five-year period For crash clusters (segments), crash sites should be relatively close and have similar crash causes

21 Selection of Safety Improvement Locations

22 Picking the Highest Priority Locations for Analysis District Priority Improvement Areas DistrictRegionalStatewideInterstateTotal Total

23 3. Diagnosis of Safety Problems 23

24 Steps in Determining Crash Causality Examine safety records Identify physical features of roadway Identify traffic operating characteristics Consider information from Human Factors Guidelines

25 Crash Diagnosis (Crash Causality)

26 Example Safety Improvement Location US MP to MP – District 1

27 Site Characteristics Rural setting 45-mph curve in middle of segment Intersection located at end of 45-mph curve Highway is relatively straight to north and south of segment

28 Crash Characteristics Total of 17 crashes Crashes can classified into three groups: Crashes on 45-mph curve (12 crashes) Crashes at intersection (2 crashes) Crashes on straight sections on either side of curve (3 crashes)

29 Crash Characteristics (Crashes on 45-mph Curve) Lack of driver awareness of curve and curve characteristics was a contributing factor in over half of the crashes (i.e., inattention, speed too fast, drove left of center, overcorrection) Eight out of 12 crashes occurred in ascending direction In eight out of 12 crashes, vehicle ended up off of roadway (i.e., outside of ROW, in ditch, on embankment, etc.)

30 Crash Characteristics (Crashes at Intersection) Speed too fast for conditions was contributing factor in both crashes In both crashes, vehicle ended up off of roadway (i.e., in ditch or embankment)

31 Crash Characteristics (Crashes on Straight Sections) No apparent pattern, other than all of the crashes occurred on icy road surface with speed too fast for conditions

32 Roadway Environment 45-mph curve is at bottom of relatively steep downgrade (-2.6%) in ascending direction

33 Roadway Environment Curve is signed in advance with combination horizontal alignment/advisory speed signs Chevrons and post- mounted delineators are located on curve Intersection warning sign located on curve Narrow shoulder widths – 2 feet 2 ft. shoulder

34 Roadway Environment No left-turn lane at intersection Narrow approach and lane widths on minor road at intersection – 20 feet

35 Roadway Environment CMF for horizontal curve is 1.48 CMF for narrow shoulder widths is Composite CMF for this section is 1.734

36 Traffic Operating Environment No other locations for several miles to north and south where drivers must slow down – either straight sections or wide radius curves 60 mph speed limit, so many vehicles likely traveling at 65 mph+

37 Human Factors HFG indicates that driver expectations about a curve are an important factor in drivers’ judgments about the curvature and corresponding speeds Expectations, in turn, are significantly influenced by drivers’ experience with previous curves and tangents HFG also states that advisory/message signs should not be placed on curves – direct information only should be provided via lane markings, raised markers, etc.

38 Diagnosis In curve crashes, there was inadequate driver awareness of the curve and curve characteristics This was likely influenced by the lack similar curves on both sides of this section (previous driver experience) Misjudgment of speed on curve in ascending direction could also be affected by downgrade prior to curve

39 Diagnosis Narrow shoulders likely contribute to the high percentage of vehicles ending up to side of the highway This limits the likelihood of recovery and the driver’s ability to bring the vehicle to a safe stop on the shoulder Turning crashes may be related to the higher speeds on US 95 combined with the lack of a turn lane and the narrow minor road approach

40 4. Identification of Countermeasures 40

41 Identify Crash Countermeasures

42 Alternative Countermeasures (Higher Cost) Modify horizontal curve – increase radius and length of curve, add spiral transitions Widen lanes through curve Widen shoulders through entire section Add left-turn lane at intersection Widen turn radii and lane widths on minor road at intersection

43 Alternative Countermeasures (Lower Cost) Install oversize horizontal alignment warning signs Install horizontal alignment warning signs with beacons Place large arrow signs on curve Install snowplowable, permanent raised pavement markers through curve Relocate intersection warning sign away from curve

44 Alternative Countermeasures (Lower Cost) Place wide edge line markings through curve Install continuous shoulder rumble strips Install changeable speed warning signs

45 5. Evaluation of Potential Countermeasures 45

46 Create a Simple Benefit/Cost Ratio Benefits = Reduced Annual Fatalities * Monetary Value of a Fatality + Reduced Annual Injuries * Monetary Value of an Injury Reduced Annual PDO Crashes * Monetary Value of a PDO Crash Cost = Units of Countermeasure Element * Cost Rate for Element B/C Ratio = Annual Monetary Value of Crash Reduction/ Annualized Cost of Countermeasure 46

47 Monetary Impact of Crashes Fatalities $6,053,567 Serious Injuries $301,473 Visible Injuries $84,441 Possible Injuries $55,972 Property Damage Only$6,480 47

48 Sample Cost Rate CMF 2r Shoulder Width/Type Length of roadway to modify Additional width of shoulder Shoulder type Unit Cost Rate - $33,333/mile-feet of shoulder width for paved shoulder (Based upon $400,000 a lane mile) 48

49 Sample Cost Rate CMF 3r Horizontal Curves (Length, Radius, Spiral) Desired Length Terrain type Unit Cost Rate - $/Curve (by type of terrain – flat, rolling, mountainous) $50,000/flat curve $100,000/rolling curve $400,000/mountainous curve 49

50 Range of B/C Ratios CountermeasureRangeAverage High B/CProtected Left-turn Signal to Dynamic Speed Warning29.41 to Left-turn Lanes10.86 to Chevron signs for Curves37.25 to Right-turn Lanes12.19 to Consolidate Driveways6.74 to Roundabout0.45 to Widen Shoulders0.27 to Modify Curve0.26 to Convert to two 'T' Intersections0.33 to Add a passing lane0.34 to Reduce Skew Angle0.11 to Increase Median0.94 to Reduce Speed Limit0.01 to Low B/CWinter Maintenance0.04 to

51 Sample Countermeasure Information 51

52 Remaining HSCA Steps 52 Complete Identification of improvement options (countermeasures) Evaluate Benefits of Improvement Options using the HSM procedures Estimate B/C Ratios Evaluate Project Priorities Final Assessment of Process

53 5. Summary of Benefits 53

54 HSCA Benefits for Districts Within each district, helps ensure that highest need locations are being addressed Represents an accepted, defensible and repeatable process Uses latest techniques for identification of crash causality and countermeasures (HSM and HFG) Relatively low-cost to apply – all data is already available from existing sources such as TAMS, WebCARS, and video logs 54

55 More HSCA Benefits for Districts Information on countermeasures can be used as a first step in the project development process Analysis files serve as an historical record for safety improvement identification process Input data forms a rich database that can be used for other purposes within districts 55

56 HSCA Benefits Agencywide Places ITD in-line with FHWA directives for data- driven, performance-based safety decision-making processes Helps ensure best return statewide on scarce safety improvement dollars Process is consistent with and can be integrated with other statewide initiatives underway such as ICAPS, statewide travel model, TAMS, and IPLAN Process removes bias from allocation of safety dollars across the state 56


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