How does ACAS X improve on traditional TCAS?

ACAS X (Airborne Collision Avoidance System X) is the next-generation collision avoidance standard. Improvements: Probabilistic model using dynamic programming (optimizes resolution advisories against encounter model), Reduced unnecessary alerts while maintaining safety, Better coordination with ATC procedures, Extensible to new surveillance sources (ADS-B), and Variants for different operations (Xa for large aircraft, Xo for unmanned). ACAS Xa uses existing Mode S transponders but with improved logic. Expected benefits: 25% reduction in operational impact (fewer RAs), Maintained or improved safety margin, and Better compatibility with new procedures (parallel approaches). Currently in validation; deployment expected to replace TCAS II over coming decade.