This project, funded by Arizona Department of Transportation (ADOT) aims to identify potential data errors that may occur in the ADOT traffic stations in order to further improve data quality. The methods developed for error identification will be implemented in a computer program to assist TOC’s staff in repetitively examining the data quality and potential causes. The project will focus on the data collected within the I-10 segment between Loop 303 and Loop 202 and the I-17 corridor in in Phoenix. The major benefits of this project are: 1) traffic engineers make much more precise decisions in traffic operation strategies (mitigating congestion), and 2) road users can receive more accurate travel time information and be more satisfied with ADOT’s services.