Usually the marine terminal will then install a computer system to replace the paper filing system. A computer system gives more people access to the same data without the physical interference problems associated with the paper system. The marine terminal can then continue to add personnel to the tracking effort as the inventory and handling volume increases.

Office Needs

The first computer system a marine terminal installs usually addresses only the office needs and it is still separated from the yard handling equipment in the marine terminal by a paper system. For instance, work lists are entered into the computer by office personnel and are printed out for the equipment operator to follow. In the automation hierarchy, the office computer system is considered a Level-3. The personnel operating the handling equipment are substitutes for the Level-2 and Level-1 computers.

The Problem Evolves

Invariably the inventory recorded in the office computer and the inventory actually in the yard are different. An error in the computer's inventory will create an error on the work list. The error on the work list will force the equipment operator to select a yard position for a container different from the position on the work list. The equipment operator will record the change on the paper work list and after the list has been completed it will be returned to the office. Office personnel will attempt to correct the inventory in the computer from the corrected work list. Due to other inaccuracies in the computer's inventory, a certain number of these corrections will be rejected by the computer as inconsistent.

The Dilemma

At this point the office personnel can usually ignore the inaccuracies in the computer. As the volume of containers increases, however, it is not unusual for an inventory system of this type to be as much as 20% inaccurate. When the inaccuracies become intolerable, the terminal operator has several methods to correct the problem:

• Routinely have yard personnel perform manual inventories of either the entire facility or areas of the facility and enter the inventory information into the computer system to bring it up to date.
• Add mobile yard personnel to locate lost containers required for immediate delivery to either a truck or a vessel; that is, containers in positions different from the position recorded in the computer.

Both of these solutions continue to increase the amount of nonproductive labor in the terminal. As the volume increases and as more ships are processed, the handling equipment operators are more likely to shuffle containers around at the end of each ship in order to get the ship off berth. Eventually the manual inventories and the staffing required to locate containers becomes inefficient and expensive. There are two steps to correct this problem:

1. Place computer CRT terminals in the handling equipment to reduce the lag between the time a work list is given to the equipment operator and the time it is entered and confirmed in the computer.
2. In addition to installing CRT terminals, instrument the handling equipment so that the machine can determine its location in the marine terminal and report its position directly to the computer without any human intervention.

The method selected will depend on the quality of the labor available at the facility. If the labor quality is good, there is little economic incentive for the higher cost step of instrumenting the handling equipment. The CRT and instrumentation installed in the handling equipment is usually connected to the Level-3 computer with some variation of a radio system, although other methods have been successfully employed [reference 4].

The Benefits

For marine terminals installing a Level-3 computer system, the following beneficial effects were reported by at least 50% of the marine terminals responding to a recent survey [reference 5]:

• The dwell time for import containers is reduced.
• The necessary sorting, checking, and forwarding of documentation is easier.
• Overall administrative costs are lower.
• The available space in the container yard is used more efficiently.
• The turn round time for equivalent sized vessels is reduced.
• The average waiting time for vehicles to be serviced at the import/export grid is reduced.

Productivity increases have been noted for advanced passive tracking Level-3 computers in several other areas [reference 6]:

• vessel planning
• yard operation

Historically, vessel planning is a trial and error process. Once a plan is made, it usually remains unchanged because of the burden of paperwork associated with a new plan; the cargo center of gravity must be recalculated and a new stow plan produced. If the computer performs these functions, then the planner has the extra time and the incentive to obtain the best possible loading on the vessel. In addition, the planner can tune the center of gravity of the vessel to reduce its fuel costs between ports.

When the handling equipment operator can receive the worklist on a CRT, then it is much easier for planning personnel to change the work list. This is usually critical in the final stages of ship loading, when the plan changes must be given to the handling equipment operator in a timely and accurate manner.

The most advanced realization of these two concepts are the color graphic planning systems [reference 7-8]. In these systems, the containers are drawn on a color CRT screen. The planner uses a pointing tool to indicate which containers are to be moved and where they should go. The computer then creates the work list and transmits the list to the CRT in the handling equipment for execution.