Maintenance access zones for storage and retrieval systems

A maintenance access system for a storage and retrieval system having a storage and retrieval space and automated transport vehicles disposed in the storage and retrieval space, the maintenance access system comprising:

• at least one maintenance access control unit associated with a portion of the storage and retrieval space;
• at least one barrier located in the storage and retrieval space and defining a boundary of the portion of the storage and retrieval space, the at least one barrier being configured to substantially prevent the passage of the automated transport vehicles past the at least one barrier;
• and
• a controller connected to the maintenance access control unit, the controller being configured to receive a signal from the at least one maintenance access control unit for isolating the portion of the storage and retrieval space associated with the at least one maintenance access control unit, where the controller in response to the signal closes the at least one barrier isolating the portion of the storage and retrieval space and effects the removal of operative automated transport vehicles from and shutting down of inoperative autonomous transport vehicles within the portion of the storage and retrieval space while allowing continued operation of autonomous transport vehicles in other portions of the storage and retrieval space.