1. Interactive Highway Safety Design Model (IHSDM) By Josh Hinds

2. The Modules Outline Background of IHSDM Description of the Modules New Features An IHSDM Project from Start to Finish Future Developments Conclusion

3. Background What is IHSDM? IHSDM is a suite of software analysis tools that evaluate the safety and operational effects of the geometric design on two-lane rural highways. (www.ihsdm.org)www.ihsdm.org

4. Background What is IHSDM? Safety analysis tool, not specifically used for designing. Evaluates the geometric design of the highway. Two-lane rural highways Compares user inputted design to designated design standards.

5. The Modules Why Was IHSDM Needed? 77% of the Nation’s highways are two-lane rural highways 41% of all the fatal crashes occur on two- lane rural highways Citizens demand increased safety on two-lane rural highways

6. Background Why Was IHSDM Needed? The highway network is getting older. Stakeholders are expecting safer highways on the same budget. Highway designs need to be checked for safety ‘black spots’.

7. Background How Does IHSDM Help? Makes use of five software modules that analyze the geometric design of the highway – Policy Review – Crash Prediction – Design Consistency – Traffic Analysis – Intersection Review

8. Background Framework of the IHSDM Program IHSDM Policy Review Crash Prediction Design Consistency Traffic Analysis Intersection Review (Coming Soon) IHSDM is composed of these modules.

9. Background How Does IHSDM Work? The user inputs the design file. The five modules compare the inputted design values to the AASHTO policy standard values. IHSDM determines how far out of range the values are and provides feedback to the user.

10. Background How Can IHSDM Benefit the Designer? Intended to be used throughout the design process. Can be used on new construction and existing facilities. Provides a Quality Assurance check throughout the design process.

11. Background How Can IHSDM Benefit the Designer? Find ‘Accident Black Spots’ before construction. Save money by lowering crash rates and eliminating the reconstruction of unsafe areas. Double check design values. Uses design software format.

12. Background How Can IHSDM Benefit the Designer? Helps project developers improve the expected safety performance of the final design. Justifies and defends geometric design decisions.

13. Background How Can IHSDM Benefit the Designer? - AASHTO A Policy on Geometric Design of Highways and Streets "Green Book" - AASHTO Roadside Design Guide - AASHTO Guide for Development of Bicycle Facilities - Numerous Editions and Metric/English

14. Background How Can IHSDM Benefit the Designer? Public perception that the roadway is ‘safe’. Estimates the expected crash frequency for the geometric design. Analyzes other safety and operation performance measurements. (SSD, superelevation, etc.) (Turner-Fairbank)

15. Background What is ‘Safe’? Every roadway will have crashes. ‘Safe’ (past) – Meeting a minimum set of design criteria. ‘Safe’ (presently) – Comparison of number of crashes to sites with similar characteristics. (FHWA, Paniati)

16. The Modules FHWA was in charge of all the research FHWA received input from numerous state agencies, consulting firms, and academic institutions. Based on research received from field data.

17. The Modules Policy Review Module Automates the process of checking geometric design elements against relevant design policy standards. Construction or Reconstruction Quality Assurance / Quality Control

18. The Modules Policy Review Module Cross Section (traveled-way, auxillary, shoulder) Horizontal and Vertical Alignment Sight Distance Items with an asterisk will be compared to FHWA standards.

19. The Modules Policy Review Module Summary of what will be analyzed

20. The Modules Policy Review Module Results

21. The Modules Crash Prediction Module Identifies improvement projects on existing highways Estimates the frequency and severity of crashes. Compares the safety performance of design alternatives Will assess that safety cost effectiveness of design decisions.

22. The Modules Crash Prediction Module Uses the Empirical Bayes Method Algorithm for estimating crashes combines base models and accident modification factors Highway segments and intersections – 3-leg stop control on the minor – 4-leg with stop control on the minor – 4-leg signalized

23. The Modules

24. Crash Prediction Module - The crash history

25. The Modules Crash Prediction Module Table – Crash Rate By Design Element By Segment – Crash Type Graph – Expected Frequency – Crash Rate By Design Element By Segment

26. The Modules Crash Prediction Modulus Module provides a comment section to inform the user of any areas not addressed. Summary of what will be analyzed, and how the results are formatted. Module runs analysis.

27. The Modules Crash Prediction Modulus Results

28. Expected Crash Type Distribution Crash TypeHighway SegmentsIntersectionsTotal Single-vehicle accidents Collision with animal16.6 (23.03%)0.1 (0.08%)16.6 (23.11%) Collision with bicycle0.2 (0.22%)0.2 (0.25%)0.3 (0.48%) Collision with parked vehicle0.4 (0.52%)0.0 (0.03%)0.4 (0.55%) Collision with pedestrian0.3 (0.37%)0.2 (0.33%)0.5 (0.7%) Overturned1.2 (1.71%)0.1 (0.1%)1.3 (1.82%) Ran off road15.1 (20.94%)0.3 (0.48%)15.4 (21.43%) Other single-vehicle accident1.9 (2.68%)0.3 (0.41%)2.2 (3.09%) Total single-vehicle accidents35.6 (49.49%)1.2 (1.68%)36.8 (51.17%) Multiple-vehicle accidents Angle collision2.1 (2.91%)5.2 (7.26%)7.3 (10.16%) Head-on collision1.0 (1.42%)0.3 (0.46%)1.3 (1.87%) Left-turn collision2.3 (3.13%)1.6 (2.29%)3.9 (5.42%) Right-turn collision0.3 (0.45%)0.1 (0.1%)0.4 (0.55%) Rear-end collision7.5 (10.36%)6.6 (9.22%)14.1 (19.58%) Sideswipe opposite-direction1.3 (1.79%)0.4 (0.51%)1.7 (2.3%) Sideswipe same-direction1.4 (1.94%)1.0 (1.4%)2.4 (3.34%) Other multiple-vehicle collision2.2 (3.06%)1.8 (2.55%)4.0 (5.6%) Total multiple-vehicle collisions18.0 (25.04%)17.1 (23.78%)35.1 (48.83%) Total accidents53.6 (74.53%)18.3 (25.47%)71.9 (100.0%)

29. The Modules Design Consistency Module Provides a Quality Assurance check on the consistency of the design. Allows designer to double-check design assumptions. Some designs conform to policies, but can not be consistent for the drivers. Heavily focused on Horizontal Curves.

30. The Modules Design Consistency Module Drivers are more likely to make mistakes at features that violate their human inclination. Reduction of speed in tangent before horizontal curve. Design speed vs. 85 th percentile speed. Design conformance vs. driver’s expectations

31. The Modules Design Consistency Desired Speed = 85 th percentile speed 62 mph was determined by studies in six states. Tangent Speed

32. Design Speed Assumption Check (in the direction of decreasing stations) Station V85 - Vdesign Speed (mph) Condition FromToMinMax 14+281.69311+157.3036.212.02 11+157.303 10+986.32 1 0.06.21 10+986.3219+771.386(-7.1)0.04 9+771.3869+368.0380.06.21 9+368.0388+014.9646.210.22 8+014.9646+967.8165.16.21 6+967.8164+761.5726.29.72 4+761.5724+564.7310.06.21 4+564.7314+171.984(-5.7)0.04 4+171.9843+703.4610.06.21 3+703.461349.4586.212.02 349.4580.0004.36.21 Design Speed Assumption Check Conditions Key Condition 1: 0 mph <= (V85 - Vdesign) <= 6 mph Condition 2: 6 mph < (V85 - Vdesign) <= 12 mph Condition 3: 12 mph < (V85 - Vdesign) Condition 4: (V85 - Vdesign) < 0 mph where: V85 = estimated 85th percentile operating speed (mph) Vdesign = design speed (mph )

33. Speed Differential of Adjacent Design Elements Check (in the direction of increasing stations) Station of max speed on preceding element Max speed on preceding element (mph) Start Station of curve Speed on curve (mph) Speed Differential (mph) Condition 0.00054.832.80854.00.81 601.39158.8601.39158.80.01 1+727.73361.41+778.90461.20.21 2+091.46761.22+283.48160.11.11 2+283.48160.12+512.52360.7-0.61 3+015.50361.53+301.39159.32.21 3+301.39159.33+703.46160.0-0.81 4+032.47060.44+507.47042.917.53 4+507.47042.94+564.73148.6-5.71 4+788.69850.14+788.69850.10.01 4+788.69850.15+708.10055.8-5.71 6+984.26159.47+061.40458.80.61 8+025.50659.28+117.82858.70.61 9+599.35562.09+982.44454.08.02 10+325.36154.010+533.71742.811.22 11+797.93659.111+797.93659.10.01 12+359.02162.012+861.28656.25.81

34. The Modules Traffic Analysis Module Evaluates the operational effects of the current and future traffic estimates. Can be used to determine the effects of alternatives. (realignment, cross-section improvements, and additional passing lanes) Construction or Reconstruction

35. The Modules Traffic Analysis Module Uses the TWOPAS rural traffic simulation model for two-lane highways. QC/QA Provides documentation for design exceptions Determines the time following other vehicles

36. The Modules Traffic Analysis Module Traffic Flow Traffic characteristics Highway Elements Time Parameters Results

37. Traffic Output Data / Main Section (16.404 to 14+116.404 increasing; 14+116.404 to 16.404 decreasing) Traffic Output Data Direction of Travel Increasing Station Decreasing StationCombined Flow Rate from Simulation (v/hr)299303602 Percent Time Spent Following (%)39.644.942.3 Average Travel Speed (mph)52.151.351.7 Trip Time (min/veh)3.1 Traffic Delay (min/veh)0.120.220.17 Geometric Delay (min/veh)0.310.260.29 Total Delay (minutes/vehicle)0.430.490.46 Number of Passes000 Vehicle mi Traveled7978081,605 Total Travel Time (veh-hrs)15.315.731

38. The Modules Traffic Analysis Module TWOPAS – Traffic Simulation Model – User can specify traffic demand and vehicle mix. – Also, can specify horizontal and vertical alignment. – Models 13 types of vehicles with performance characteristics for each.

39. The Modules Intersection Review Module Not currently used in the 2006 edition. Research and module are complete. Still in the final testing phase. Expect the Intersection Review module to be released very soon as an update to the 2006 edition.

40. The Modules Intersection Review Module Diagnostic review of the expected performance. Uses the ‘Expert System’ Stopping Sight Distance Corner radius and turn lane design.

41. The Modules The future of IHSDM IHSDM is constantly being updated for the newest standards. Research and data collection continues for all modules. Additional modules are being researched and created. (intersection review) Multi-Lane highways

42. The Modules Conclusion