Safety Performance Indicators (SPIs) are measurable metrics monitoring and evaluating ADS safety in operation, including lagging indicators recording outcomes like crashes and injuries, and leading indicators capturing precursors like near misses and risky behaviours. Research tested time-based and distance-based SPIs on the SHRP2 dataset containing 1402 crashes and 5262 near-crashes, achieving Area Under the Curve values of 0.883 for Distance Headway and 0.832 for Time-to-Collision in distinguishing crashes from normal driving. SPIs support safety cases, in-service monitoring and reporting requirements, and continuous ADS deployment monitoring, with future work extending analysis to additional datasets and field data collection.