Recognizing that the agriculture industry continues to have the highest worker fatality rate, a multi-year teacher professional development was conducted to improve teachers' tractor and machinery safety knowledge. The purpose of this study was to analyze participant knowledge throughout the professional development to better understand the role of continued engagement. A total of 97 teachers participated in year five of the five-year training program. Participant gender identification was nearly equal in terms of male and female. Beginning (0-2 years of experience) and mid-career (3-5 years of experience) educators accounted for over 80% of participants, with most participating in the training program during multiple years. This program utilized the National Safe Tractor and Machinery Operations Program (NSTMOP) curriculum. The average post-test score was 39 out of 50. Second-year attendees recorded the lowest test score average, while fifth-year attendees recorded the highest. On the post-test, participants were asked what attracted them to return to the training experience. Almost one-third reported that curriculum obtainment was the primary attractor. This study has implications for professional development coordinators looking to implement safety education programs. Future research should focus on evaluating the implementation of safe tractor and machinery operations in participating teachers' classrooms.