Effective planning remains the cornerstone of any successful infrastructure project delivery. Large construction projects typically operate across two interconnected levels of planning: a macro-level master program, often built in Primavera P6, and a micro-level short-term plan, developed in tools such as Aphex or Microsoft Project. Despite their shared purpose, these systems are frequently disconnected. This results in misaligned data, inconsistent reporting, and reduced confidence in the overall project schedule.

This paper proposes an optimised Macro–Micro Planning Interface Protocol (MM-PIP) that establishes a logical and data-driven bridge between the two planning levels. The framework defines consistent Levels of Detail (LoD), aligns Work Breakdown Structures (WBS) with Cost Breakdown Structures (CBS), and sets clear governance rules for progress integration and performance measurement. Drawing from ISO 21511, PMBOK (7th Edition), AACE Recommended Practices, and practical experience on major Australian infrastructure projects, this study demonstrates that a systematically defined interface significantly improves reporting clarity, schedule reliability, the overall project control and performance management.