A terminal operating system (TOS) is the software that runs a container terminal. It decides where each container is stacked in the yard, which crane lifts it, in what order the ship is unloaded and loaded, and when a truck may collect it. A container terminal is the part of a port where container ships berth. A large terminal handles thousands of containers a day.
Every container is a steel box of a standard size, usually 20 or 40 feet long. Port traffic is counted in TEUs, or twenty-foot equivalent units: one 20-foot container is one TEU, and one 40-foot container is two. In the yard, containers are stacked five or six high in long rows. If a container that is needed now sits at the bottom of a stack, the yard machines must first move the boxes on top of it. These extra moves waste time and fuel. So the main job of the TOS is to put each container where it will be easy to reach when it is next needed.
Take, for example, a container ship that berths at a terminal in Visakhapatnam with 1,800 containers to unload and 1,500 to load. Before the ship arrives, the TOS reads the shipping line's list of containers and where each one sits on board. The line's planners decide where the export boxes will go on the ship. The TOS turns both lists into a work sequence for each of the four quay cranes, the large cranes along the berth. As each import container comes off the ship, the TOS shows the driver of a yard machine, on a screen in the cab, where to stack it. Boxes that customs wants to examine go to a separate area. Boxes whose customs clearance is complete are given a time slot for a truck to collect them at the gate. The ship sails 30 hours after it berthed.
The TOS records every move. A forwarder's freight forwarding software and a supply chain visibility platform read these records to learn when a container was unloaded, released and taken out of the gate. The terminal uses the same records to bill the shipping line for each crane move, and to charge storage for a container that stays too long.
Safety is a large part of the work, because a terminal mixes heavy machines, trucks and people. Some terminal software also records safety checks, permits for dangerous work and accidents. Many terminals now add automated cranes and remote-controlled yard machines, which the TOS directs. The TOS sits where the sea leg of ocean freight and customs meets the land leg, which is covered on the page on road freight.