ABSTRACT A COMPARATIVE EVALUATION OF CRASH DATA QUALITY IDENTIFICATION METHODS MAY 2008 ARIANNA M. MICKEE, B.S.C.E., UNIVERSITY OF MASSACHUSETTS AMHERST M.S.C.E, UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Michael A. Knodler, Jr. Throughout the United States federal and state agencies use crash data in order to properly plan safety improvements within their areas. Unfortunately since 2000, transportation professionals have noticed a significant lack of reliable crash data in some states. These issues have a multitude of causes and therefore there are many solutions to these issues. In order to determine what courses of action need to be taken in order to address these issues, many state and federal government agencies have been conducting studies using various methods. This thesis compares three basic methods used to identify crash data quality issues facing transportation professionals. The three methods evaluated are surveys, audits and focus groups. These three methods are currently practiced by professionals to gain insight to crash data quality issues. Unfortunately, the methods are often used inappropriately and inefficiently to determine data quality issues. The purpose of this thesis is to describe what valuable information can be obtained by using these methods as well as what information cannot be obtained. The results of three projects were employed in the evaluation of these methods. These projects include the Massachusetts Highway Departments Crash Data Quality Project, the Commercial Motor Vehicle Crash Data Quality Project, and finally, the Police Outreach Survey. In the end, these projects help determine the usefulness of these methods in terms of their ability to identify data quality issues and efficient and cost effective solutions to address these issues.