USA Banner
  U.S. flag
              An official website of the United States government Here's how you knowOfficial US Government Icon
              **Official websites use .gov**A **.gov** website belongs to an official government organization in the United States.
            Secure Site Icon
              **Secure .gov websites use HTTPS**
                  A **lock** ( A locked padlock ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. 
 U.S. Department of Transportation Icon United States Department of Transportation
 Search DOT
            Search
                    About FHWAFHWA Organization
                Headquarters Offices
                Field Offices
                Strategic Plan
                Business Opportunities
                Staff Directories
                Careers
                Highway History
                Contact UsProgramsAcquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                Safety
                Browse by TopicsResourcesCore Highway Topics
                Federal Aid Essentials
                Automation
                Complete Streets
                Laws and Regulations
                Policy & Guidance Center
                Section 508
                Publications and Statistics
                Professional Development
                National Highway Institute
                Resource Center
                Accessibility Resource Library
                FHWA Research LibraryNewsroomPress Releases
                Speeches & Testimony
                Photos
                Videos
                Media ContactsMenu OFFICE OF RESEARCH, DEVELOPMENT, AND TECHNOLOGY AT THE TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Home
                        Research


            
            In This Section
        Explore Research and Technology
                HSIS Home
                Program History
                                Background
                Participating States
                Laboratory
                PBCAT App
                                Pedestrian and Bicycle Crash Analysis Tool
                Getting Started
                Crash Typing
                Features
                User Guide
                Support Images
                Products
                                Product Overview
                HSIS Summaries
                Research Reports
                Technical Summaries
                Journal Citations
                Safety Analysis Tools
                Other Products
                Data
                                Data Overview
                State Statistics
                Data Elements
                Guidebooks
                Resources
                Ongoing Research
                Contact
                Liaisons
                Site Map
                
                Difficulties with Quasi-Induced Exposure when Speed Varies Systematically by Vehicle Type
Publication Information
              Publication External Link:Link not available
              Publication Type:Article
                      Abstract:The attractiveness of quasi-induced exposure lies in the simplistic nature of its theory and application. As opposed to vehicle miles of travel, quasi-induced exposure is developed solely from the accident data themselves. Involvement ratios (IRs) are used to describe the relative over- or under-involvement of different drivervehicle combinations in traffic accidents. The issue of systematic bias in the involvement ratios is explored, and it is shown both theoretically and empirically that the variation in average speeds between vehicle types can affect relative accident involvement ratios. For vehicle types that routinely travel faster, the IRs will likely be underestimated; while for slower-moving vehicle types, the IRs will be overestimated. In the case of speed, the magnitude of the effect on the IRs is dependent both on the magnitude of the speed differential and the percentage of slower vehicles in the traffic stream.

Conclusions can be extended to whenever there are speed or other behavior disparities associated with the drivervehicle combinations in the traffic stream. Other examples include the speed discrepancy caused by different drivers (e.g., younger versus older drivers). Caution must be used in interpreting results from applications of the quasi-induced technique whenever such biases might be encountered.
              Publishing Date:July 2007
                                                  FHWA Program(s):Research
              Safety
              AMRP Program(s):FY 2002-2022
              FHWA Activities:Highway Safety Information System
              Subject Area:Safety and Human Factors U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

202-366-4000Subscribe to email updates
                    About
  

        
              About FHWA
                Careers
                Org Chart
                Staff Directories
                Work with UsPrograms
  

        
              Acquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                SafetyPolicies, Rights, Legal
  

        
              About DOT
                Accessibility
                Budget and Performance
                Civil Rights
                FOIA
                Information Quality
                No FEAR Act
                Office of Inspector General
                Privacy Policy
                USA.gov
                Web Policies and Notices
                Web StandardsNews & Events
  

        
              Newsroom
                Press Releases
                Speeches & Testimony
                Media Contacts
                Connect with Us