Highway safety decision-makers require timely access toquality data from a wide variety of sources. The Massachu-setts data warehouse and Interactive Data Retrieval System(IDRS) were developed to provide state and federalhighway safety decision-makers with access to a varietyof safety-related data through a common user interface that allows users with varying levels of data analysis skill toquery data. The Massachusetts data warehouse currentlyhouses 13 data sets and provides online access to nine of those data sets through the IDRS.Upon implementation of the original system, theGovernor’s Highway Safety Bureau (GHSB), which fundedthe project, and the Massachusetts Traffic Safety ResearchProgram (MassSAFE) at the University of MassachusettsAmherst, which developed the system, requested a study todetermine if the system met user needs, and what changescould be made to improve usability.