This causal-comparative and correlation study investigated the costs of runway incursion safety improvements in relation to their effectiveness to assess potential aviation system benefits.Two airports (Los Angeles International and Dallas-Ft. Worth International), which were early adopters of Runway Status Lights (RWSL), a runway incursion technology, were targeted in this analysis. Findings indicated that there were no significant differences in counts or rates of Category A, B, and D incursions at LAX and DFW when comparing the time periods before versus after RWSL installation. Category C counts and rates were found to have increased significantly after RWSL installation. The findings of this study outline the importance of assessing empirically-based impacts of large investments in aviation safety prior to implementing them system-wide. The findings do not support the premise that RWSL has improved safety at either LAX or DFW airports. Suggestions for future research are also outlined.