The ever increasing demands on the national infrastructure, along with the age, neglect, and misuse of many bridges throughout the country, have placed a great deal of strain on the States Departments of Transportation to maintain the country's bridges. While the current visual inspection process is able to access more obvious maintenance and repair needs, a more quantitative inspection will allow for a better understanding of bridge behavior and a more uniform inspection process. The In-Service Bridge Monitoring System (ISBMS) developed at the University of Delaware was designed with this process in mind. In this research, the ISBMS is used to gather strain data for up to two weeks on bridges throughout the state of Delaware. The in-service data is then used to project the maximum strain expected for a given return period. Rating factors based on the projected values are then calculated. Weigh-in-Motion (WIM) data is also collected for a number of the bridges in this study. The WIM data is used to find a correlation between truck weights and measured strain. After a correlation is found, rating factors based on the WIM data are then calculated. The in-service and WIM rating factors are finally compared to the rating factors used by the Delaware Department of Transportation and calculated in Bridge Rating and Analysis of Structural Systems (BRASS). The analysis in this study proves the usefulness of implementing the ISBMS into the routine biennial inspection process. The data gained from the system is invaluable in evaluating the overall safety of bridges. The conservative nature of the current rating factor equations is also revealed. By collecting in-service data, states will have a better understanding of their bridges under site-specific loading. This will allow for a better allocation of the limited time and funds available for bridge maintenance and repair. By implementing in-service monitoring into the current inspection process overall bridge safety and infrastructure reliability will be improved.