Interactive Highway Safety Design Model (IHSDM)

Crash Prediction Module Engineer's Manual

Developed for
Federal Highway Administration
Office of Safety Research and Development
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA 22101

Developed by
ITT Corporation, Systems Division
P.O. Box 15012

Contract No.

Developer Release
Version 4.00

Dec 17, 2007


Disclaimer

This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its content or use thereof. This document does not constitute a standard, specification, or regulation.

The United States Government does not endorse products or manufacturers. Trade and manufacturers' names may appear in this document only because they are considered essential to the objective of the document.

Limited Warranty and Limitations of Remedies

This software product is provided "as-is," without warranty of any kind-either expressed or implied (but not limited to the implied warranties of merchantability and fitness for a particular purpose). The FHWA and distributor do not warrant that the functions contained in the software will meet the end-user's requirements or that the operation of the software will be uninterrupted and error-free.

Under no circumstances will the FHWA or the distributor be liable to the end-user for any damages or claimed lost profits, lost savings, or other incidental or consequential damages rising out of the use or inability to use the software (even if these organizations have been advised of the possibility of such damages), or for any claim by any other party.

Notice

The use of the IHSDM software is being done strictly on a voluntary basis. In exchange for provision of IHSDM, the user agrees that the Federal Highway Administration (FHWA), U.S. Department of Transportation and any other agency of the Federal Government shall not be responsible for any errors, damage or other liability that may result from any and all use of the software, including installation and testing of the software. The user further agrees to hold the FHWA and the Federal Government harmless from any resulting liability. The user agrees that this hold harmless provision shall flow to any person to whom or any entity to which the user provides the IHSDM software. It is the user's full responsibility to inform any person to whom or any entity to which it provides the IHSDM software of this hold harmless provision.

Table of Contents

1.  Introduction
1.1  Overview of IHSDM
1.2  Overview of Crash Prediction Module
1.3  Purpose and Organization of this Manual
2.  Data Input Requirements
2.1  Evaluation Data
2.2  Geometric and Traffic Control Data
2.3  Traffic Volume Data
2.4  Crash History Data
3.  Crash Prediction Procedural Elements
3.1  Segmentation Procedure
3.2  Base Models (Segments and Intersections)
3.3  AMFs (Segments and Intersections)
3.4  Calibration Factors
3.5  Crash Prediction When Site-Specific Crash History Data are Available
4.  CPM Output
4.1  Highway Data
4.2  Evaluation Report
5.  Crash Prediction Algorithm
6.  AMFs for Highway Segments
6.1  Lane Width (AMF1)
6.2  Shoulder Width and Type (AMF2)
6.3  Horizontal Curve Length, Radius, and Presence or Absence of Spiral Transition (AMF3)
6.4  Superelevation (AMF4)
6.5  Grades (AMF5)
6.6  Driveway Density (AMF6)
6.7  Passing Lanes and Short Four-Lane Sections (AMF7)
6.8  Two-Way Left-Turn Lanes (AMF8)
6.9  Roadside Hazard Rating (AMF9)
6.10  Reference
7.  AMFs for Intersections
7.1  Intersection Skew Angle (AMF10)
7.2  Intersection Traffic Control (AMF11)
7.3  Intersection Left-Turn Lanes (AMF12)
7.4  Intersection Right-Turn Lanes (AMF13)
7.5  Intersection Sight Distance (AMF14)
8.  Examples
8.1  Example 1: Applying the Sliding Scale Analysis
9.  Default Tables
9.1  Default Percentage Distributions for Crash Severity Level and for Crash Type and Manner of Collision
9.2  Default Percentage Distributions for Crash Type and Manner of Collision on Rural Two-Lane Highways
10.  Calibration Procedure
10.1  Calibrating the Roadway Segment Crash Prediction Algorithm
10.2  Road System to be Used in Calibration Process
10.3  Level 1 Calibration Process for Roadway Segment Crash Prediction Using ADT Only
10.4  Level 2 Calibration Process for Roadway Segment Crash Prediction Using ADT, Lane Width, and Shoulder Width
10.5  Calibrating the At-Grade Intersection Crash Prediction Algorithm
10.6  Calibration of Crash Severity Distribution
10.7  Calibration of Crash Type Distribution
10.8  Calibration Factors for Sub-areas within a State
10.9  Local Calibration Factors
11.  Glossary
Index

List of Tables

1.  Overdispersion Parameters for Base Models
2.  Values of AMF for Lane Width of Highway Segments (AMFra)
3.  Values of AMF for Shoulder Width of Highway Segments (AMFwra)
4.  Accident Modification Factors for Shoulder Effective Width (SEW) and Shoulder Type on Two-Lane Highways (AMFtra)
5.  Design Superelevation (edesign) as a Function of Maximum Superelevation Rate, Curve Radius (emax=0.04) and Design Speed (V mi/h)
6.  Design Superelevation (edesign) as a Function of Maximum Superelevation Rate, Curve Radius (emax=0.06) and Design Speed (V mi/h)
7.  Design Superelevation (edesign) as a Function of Maximum Superelevation Rate, Curve Radius (emax=0.08) and Design Speed (V mi/h)
8.  Design Superelevation (edesign) as a Function of Maximum Superelevation Rate, Curve Radius (emax=0.10) and Design Speed (V mi/h)
9.  Design Superelevation (edesign) as a Function of Maximum Superelevation Rate, Curve Radius (emax=0.12) and Design Speed (V mi/h)
10.  Accident Modification Factors for Installation of Left-turn Lanes on the Major Legs to Intersections
11.  Accident Modification Factors for Installation of Right-turn Lanes on the Major Legs to Intersections
12.  Accident Modification Factors for Intersection Sight Distance Limitations in Quadrants of Three-Leg and Four-Leg Intersections with Minor STOP Control
13.  Default Percentage Distributions for Crash Severity Level and for Crash Type and Manner of Collision
14.  Default Percentage Distributions for Crash Type and Manner of Collision on Rural Two-Lane Highways
15.  Minimum Requirements for Calibration Level 1 and Level 2
16.  Data Needs for Calibration Level 1 and Level 2
17.  Estimate Mileage by ADT Level and Horizontal Alignment
18.  Estimate Mileage by ADT Level and Vertical Alignment
19.  Horizontal Alignment Defaults from HSIS Data
20.  Vertical Alignment Defaults from HSIS Data
21.  Estimate Mileage by ADT Interval
22.  Estimate Proportion of Mileage by Terrain
23.  Weighted Average Curve Length1
24.  Default Values for Level 1 Calibration
25.  Predicted Annual Non-Intersection Crashes as a Function of ADT
26.  Estimates Required for Alignment Component
27.  Estimate Mileage by ADT Level and Vertical Alignment
28.  Illustration of How Average Percent Grade Can Be Applied Across Lane and Shoulder Width Combinations
29.  Estimate Proportion of Mileage by Terrain
30.  Estimate Mileage by ADT Interval, Lane Width, and Shoulder Width
31.  Default Values for Level 2 Calibration
32.  Predicting Total Non-Intersection Crashes as a Function of ADT, Lane Width, and Shoulder Width
33.  Desirable Minimum Sample Sizes by Type of Intersection
34.  Example of Desired Sample Stratification of Three- and Four-Leg STOP-Controlled Intersections Based on Major Road ADT
35.  Example of Desired Sample Stratification of Four-Leg Signalized Intersections Based on Major Road ADT
36.  Example of Desired Sample Stratification of Three-Leg STOP-Controlled Intersections Based on Major-Road ADT and Highway District
37.  Absolute Minimum Sample Sizes by Type of Intersection