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Interactive Highway Safety Design Model (IHSDM). Goal To marshal the best available knowledge about safety effects of geometrics into a more useful and.

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Presentation on theme: "Interactive Highway Safety Design Model (IHSDM). Goal To marshal the best available knowledge about safety effects of geometrics into a more useful and."— Presentation transcript:

1 Interactive Highway Safety Design Model (IHSDM)

2 Goal To marshal the best available knowledge about safety effects of geometrics into a more useful and usable form for highway project planners and designers.

3 What is the Interactive Highway Safety Design Model (IHSDM)? A suite of software analysis tools used for evaluating the safety and operational impacts of highway geometric design.

4 Intended Usage Throughout the highway design process (preliminary planning and engineering through detailed design to final review) For existing and new alignments On two-lane rural highways (2003 release)

5 Partnership State DOTs ( Arkansas, California, Illinois, Minnesota, North Carolina, Washington, and West Virginia) Software Vendors (Import data from design packages) GEOPAKCAiCE

6 Components Evaluation Modules –Policy Review –Crash Prediction –Design Consistency –Intersection Review –Traffic Analysis Basic Services

7 Policy Review Module Scope Checks roadway segment geometry against relevant design policy and “flags” variations

8 Policy Review Module Cross-section checks: –Traveled Way Width –Auxiliary Lane Width –Shoulder Width –Shoulder Type –Normal Cross-Slope –Normal Shoulder slope –Cross-Slope Rollover on Curves –Bridge Width

9 Policy Review Module Horizontal Alignment checks: –Radius of Curvature –Length of Horizontal Curve –Superelevation –Compound Curve Ratio Vertical Alignment Checks: –Tangent Grade –Vertical Curvature

10 Policy Review Module Sight Distance Checks: –Stopping Sight Distance –Passing Sight Distance –Decision Sight Distance

11 Crash Prediction Module Scope Estimates expected crash frequency based upon roadway geometry and traffic volumes

12 Crash Prediction Module –Crash prediction algorithms for: Roadway segments Intersections: –3-way STOP-controlled –4-way STOP-controlled –4-way signalized

13 Crash Prediction Module Predicts the number of crashes for a design based on the cross-section and alignment (vertical and horizontal) Calibration procedure

14 Crash Prediction Module –Roadway segment algorithm considers: AADT Lane and shoulder width Horizontal curve radius, length, spiral transition, superelevation Grade Driveway density Two-way left turn lanes, passing lanes, short four-lane segments Roadside hazard rating

15 Crash Prediction Module –Intersection algorithm considers : AADT Skew angle Traffic control Exclusive left-turn and right-turn lanes Intersection sight distance

16 Design Consistency Module Scope Estimates 85th percentile speed profile along alignment to evaluate operating speed consistency

17 Design Consistency Module Scope Estimates 85 th percentile speed profile along alignment to: –Check design speed assumption –Estimate speed reductions from an approach tangent to entering horizontal curves

18 Intersection Review Module Scope Policy Review Diagnostic Review

19 Intersection Review Module Scope Intersection Policy Review –Corner radius –Turn lane design –Intersection angle –Intersection sight distance triangles Intersection Diagnostic Review

20 Intersection Review Module Diagnostic Review Expert system that applies a systematic evaluation of an existing or proposed intersection geometric design to identify possible safety concerns and treatments –27 concerns (configuration and alignment) –Treatments include design improvements & mitigation measures

21 Traffic Analysis Module Scope Uses TWOPAS to estimate traffic quality of service measures (average speed and % time following other vehicles) Evaluates the operational performance of alternatives to passing and climbing lanes, and short four- lane sections

22 Driver/Vehicle Module Scope Driver performance model linked to a vehicle dynamics model that estimates driver speed and path, skidding and rollover potential Alpha version available Expected release in 2004

23 2003 Release 1 st public release of IHSDM May be downloaded free-of- charge from IHSDM Web site Technical support is available (see IHSDM Web site for details)

24 IHSDM Web Site

25 Training Course Pilot offerings of the IHSDM training course: July hosted by Washington State DOT in Vancouver August hosted by Central Federal Lands in Denver August hosted by Montana DOT in Helena September hosted by Wisconsin DOT in Madison September 29-October 1 hosted by Mississippi DOT in Jackson October 7-8 hosted by Maine DOT in Augusta Contact Ray Krammes: or (202)


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