An Automated Material Handling System (AMHS) that allows an overhead hoist transport vehicle to load and unload Work-In-Process (WIP) parts directly to/from WIP storage units included in the system. The AMHS includes an overhead hoist transport subsystem and a vertical carousel stocker having a plurality of storage bins. The subsystem includes an overhead hoist transport vehicle traveling along a suspended track defining a predetermined route running adjacent to the stocker, allowing the vehicle to access a WIP part directly from a storage bin. At least one storage bin includes a movable shelf operative to move laterally from a first position along the carousel path to a second position near the vehicle. The storage unit is partially open to allow the movable shelf to move to the second position, allowing the hoist to access a material unit directly from the shelf for subsequent transport along the track.