Authors: Dr. Jean-Paul Rodrigue and Dr. Theo Notteboom
Container terminals have design considerations and use equipment that vary according to their function.
1. The Design of Container Terminals
Once they started emerging in the 1960s, container terminals brought an entirely new era in port development and terminal design. One of the first impacts concerned the required footprint, which expanded. A large container terminal occupies a substantial area, mainly because of storage requirements, even if this storage is short term, usually 3 to 5 days. Where possible, early container terminals were created by converting existing general cargo terminals by tearing down on-dock warehouses to provide stacking yards. The outcome has been a wide variety of terminal configurations and a diversity between the available nautical profile and the yard footprint.
Many ports did not have enough available space to accommodate the footprint for container terminal operations, which required the setting of new facilities and new port areas. This gave opportunities to experiment with container terminal designs to improve its operations. The design and operations of container terminals take into consideration the following constraints:
- The available land footprint that will limit terminal capacity, particularly yard storage.
- The nautical profile of the site that will command maximum ship size and the number of ships that can be serviced at a given time.
- The available transport infrastructures supporting the connectivity of the terminal with its hinterland.
2. Container Terminal Equipment
To perform its operations, a container terminal relies on an array of intermodal equipment, including straddle carriers, gantry cranes, and portainers. The choice of equipment and its mix is related to a number of factors in terms of capital investment, volume, stacking density, and productivity.
- The forklift can be considered the most basic piece of intermodal equipment but has limitations and can handle only loaded 20-foot containers or empty containers of other dimensions. This is not a piece of equipment suitable for intermodal operations.
- The holstler truck is designed to move containers loaded on chassis within terminals. Although it represents a low capital investment and can move containers at high speed, it is restricted to moving containers already loaded on chassis and therefore requires other equipment.
- The straddle carrier is a flexible piece of equipment that can be used for all intermodal operations such as loading/loading railcars and trucks and stacking containers up to three in height depending on whether the straddle carrier is a 3-high or 4-high. So, depending on the straddle carrier type, the stacking density may vary between 500 and 700 TEU per hectare. Straddle carriers are often used to move containers for piers to stacks.
- The front-end loader is a more restricted piece of equipment that can reach stacks of up to three full containers and can be used for double-stack intermodal rail operations. It can also be used to manage empty stacks by reaching up to eight empty containers in height.
- The reach stacker (also known as a side loader) is also a flexible piece of equipment performing intermodal operations for rail and trucks as well as the stacking of containers. Since reach stackers are limited to stacks of three full containers (four or five empty), they can support a stacking density of 500 TEU per hectare. They are often used in intermodal rail terminals and in maritime terminals for specialized moves (e.g. reefers).
- The rubber-tired gantry (RTG) is a fixed intermodal piece of equipment that is used for loading and unloading railcars from trucks in high-density terminals as it can span over up to four rail tracks or six containers. It is also used for stacking operations to manage densities of up to 1,000 TEU per hectare with stacks of up to four full containers or five empty containers. It can service eight to nine trucks per hour, which involves 30-40 container movements since containers need to be reshuffled within their stacks. The RTG has higher acquisition costs but lower operational costs and fits well into regular container yard operations.
- The rail-mounted gantry (RMG) is a fixed piece of intermodal equipment that is widespan and can be used for intermodal operations over six to ten rail tracks, or 8 to 12 containers. While they tend to be mostly used at port terminals for operations over large container stacks, new intermodal rail terminals are increasingly relying on RMGs to perform intermodal operations over a series of train tracks, often with some below crane space for track-side stacking. Several RMG models can swivel, allowing for perpendicular crane side loading and unloading. An RMG used solely for stacking can accommodate densities above 1,000 TEU per hectare (four full or five empty containers).
- The portainer or ship-to-shore crane (STS) is a gantry crane strictly used to load and unload containerships and comes in different sizes based upon the ship class they can accommodate. While a Panamax portainer can accommodate ships up to 13 containers in width, a Post-Panamax portainer reaches up to 16 containers alongside each other. The latest class of portainers is dubbed “Ultra Post Panamax” and can handle the latest generation of containerships of 24,000 TEU by spanning up to 24 containers. The latest cranes can lift more than 150 tons at a time. Containers have to be brought to the portainer by holsters using chassis or by straddle carriers. Portainers are equipped with spreaders that have twist locks on each corner to secure the container during hoisting. Spreader technology has evolved with quite a few portainers now able to perform twin and tandem lifting. Equipment manufacturers have also tested triple lifting and systems that can handle even more containers in one move.
The ongoing automation of intermodal terminals is replacing the manually operated conventional equipment with semi or fully automated improvements. This is particularly the case for portainers, gantries, and straddle carriers, which can be remotely controlled.
3. Maritime Operations
Handling container movements at a terminal involves three segments. The first segment of the container terminal concerns maritime operations. Ship turnaround times are expected to be short, and the terminal must accommodate the schedule integrity of shipping lines. The docking area is a berth where a containership can dock with technical specifications such as length and draft. These specifications have been under pressure in recent decades as the size of containerships increased, demanding longer piers and deeper drafts. A standard post-Panamax containership of 8,000 TEU requires about 325 meters of docking space as well as a draft of about 45 feet (13 meters).
Ships of the Neo-Panamax class (12,500 TEU) require 370 meters and a draft of 50 feet (15.2 meters). Thus, a pier length of 400 meters is expected to be the right size to accommodate the largest containerships. The largest container vessels have a length overall (LOA) of some 400m, requiring a berth length of 450m. Some terminals have separate facilities for handling barges (such as Antwerp and Rotterdam), although most barges can be handled alongside the deepsea quays.
Container cranes represent the interface between the containership and the dock. Cranes have technical specifications in terms of the number of movements per hour, maximum weight, and lateral coverage. A modern container crane can have an 18-24 wide coverage, implying that it can service a containership having a width of 18 to 24 containers. A gantry crane can perform about one movement (loading or unloading) every two minutes. The larger the number of cranes assigned to the transshipment process, the faster it can take place. However, significant portside capabilities must be present to accommodate this throughput.
Aprons (Loading/unloading areas) are directly adjacent to the piers and under the gantry cranes (portainers). They are the interaction between the cranes and the storage areas where containers are either brought in to be lifted on the containership or unloaded to be immediately picked up and brought to storage areas. This is mainly done with straddlers or holsters. In the case of straddle carriers, the containers are left on the ground, while with holsters, the containers are loaded from or unloaded to a chassis. The usage of straddle carriers is more common as it enables the movement of containers directly from dockside to the stack (or vice versa). Still, terminal automation has seen the introduction of automated holsters that carry containers from the dockside to stacking areas.
4. Yard and Auxilliary Operations
Container storage represents a temporary buffer zone where containers are left while the assigned containership is available to be loaded or while waiting to be picked up for inland distribution. The larger the containerships handled by a port, the larger the required container storage yard. Container storage can be arranged by shipbound (export) and landbound (import) stacks of containers. For shared terminal facilities, stacks can even be sub-divided according to shippers. The stacking density of container storage varies depending on the selected equipment and the yard configuration.
For linear layout configurations, containers are either stored on a chassis (rare for port terminals but more common for rail terminals) or on linear stacks of two or three containers in height that can be circulated over by straddle carriers. Block layouts are serviced by rubber-tired gantry cranes or by rail-mounted (wide span) gantry cranes, enabling a higher storage density of at least four containers across (seven or eight for a wide span crane, if not more) and five full containers in height. However, higher stacking densities are linked with additional repositioning and rehandling of containers, requiring effective yard management systems. Rows of containers can be parallel or perpendicular to piers depending on the configuration and operations of the terminal.
Most terminals have a dedicated reefers (refrigerated containers) storage area where they can be plugged in, which represents, on average, about 5% of a terminal’s stacking area. Specific storage areas are also assigned to empties, which can be stacked up to seven or eight containers in height due to less stringent weight limitations. Empty container stacks are easily distinguishable from loaded container stacks because of different stacking configurations; empty stacks are higher and denser. For terminals facing capacity pressures, the tendency has been to have empty container depots outside terminal facilities. The majority of container yards also have storage for refrigerated containers, which requires specialized equipment, namely electric plugs.
A series of on-site activities support a container terminal. The management facility (administrative building) of the terminal often has a control tower to ensure a level of visibility of the terminal area. This is where many complex logistical functions are performed, such as the assignment of delivered containers to a storage space location as well as the location and the loading or unloading sequence of containers by straddlers and holsters. Additionally, the complex task of designing the loading and unloading sequence of a containership is performed. With digitalization and automation, the administration building has become the information and telecommunication nexus of the terminal.
Repair and maintenance areas are where the regular maintenance of the terminal’s heavy equipment is performed. Chassis storage areas are where empty chassis are stored while waiting to be allocated to a truck or a holster. While in North American terminals, chassis storage can take a notable amount of space because chassis are owned by pools, trucking companies own the chassis and bring them to the terminal in most of the world. The outcome is less space allocated for chassis storage. Usually, chassis are stored outside the terminal facility since chassis storage is a poor use of valuable terminal real estate.
The container freight station (CFS) can be an important auxiliary operation within the terminal. It allows for the consolidation or deconsolidation of containerized loads, with direct interaction with the container yard. The ability to access empty containers and provide loaded containers are among the key benefits of having CFS within or adjacent to a port terminal. They have become a common element of port logistics.
5. Hinterland Connectivity
Port terminals are connected to their hinterlands through inland transportation modes. The gate represents the terminal’s entry and exit point, handling up to 25 trucks at once for a large terminal facility. Truck drivers present proper documentation (bill of lading) for pick up or delivery. Most of the inspection is done remotely with cameras and intercom systems. An operator can remotely see the container identification number and verify if it corresponds to the bill of lading. Modern management systems no longer require paperwork since all the documentation is kept in an electronic format that is transmissible through secure connections. With appointment systems, the priority is to verify the identity of the truck driver, the truck, the container, and the chassis, which are all registered.
For a delivery, the truck is assigned to a specific slot at the truck drop/pick up area where the chassis holding the container will be left to be picked up by a holster, a straddle carrier, or a gantry crane for more recent terminal designs. For a pickup, the truck will be assigned to a slot in a waiting area while the container is being picked up from a storage area, put on a chassis (if the truck does not bring its own chassis), and brought to the proper slot. The truck will then head out of the terminal, be inspected to ensure that the right container has been picked up, and head inland. If this is well managed (such as by use of an appointment system), the container will already be available for pick up (on a chassis in the truck drop/pick up area). However, delays for pick up can sometimes be considerable (hours) when a large containership has just delivered a significant batch of containers, and there is a “rush” to be the first to pick them up. Therefore, substantial efforts have been made by terminal operators in recent years to improve the throughput of terminal gates through better design and with the application of information technologies, including appointment systems.
Many large container terminals have an adjacent rail terminal to which they are directly connected. On-dock or near dock rail terminals enable the composition of large containerized unit trains that reach long-distance inland markets through inland ports. An important advantage of on-dock rail facilities compared with near-dock rail facilities is that the container does not have to clear the gate of the marine terminal. In North America, since container unit trains can be very long (longer than the container port terminal facility), segments are assembled in the port on-dock rail facility and brought to a near-dock facility for full unit train assembly.
6. Conventional vs. Automated Terminal Configuration
There are two major port container terminal configurations; conventional and automated. The impacts of automation are not fully implemented on terminal operations, leading to changes in terminal configurations.
Although the function of both conventional and automated container terminals are the same (ship to shore transfer), their operations differ. In a conventional terminal, containers are brought to a pickup/drop-off area, where they will be moved to the stacking area by a holster truck or a straddle carrier. Then, they will be brought quay-side by another holster truck or straddle carrier when ready to be loaded unto a ship. The emerging automated container terminal paradigm relies on block layouts that are perpendicular to the piers. These stacking blocks are serviced by automated stacking cranes (ASC), allowing quick storage and retrieval. On the gate-side, stacks are serviced by trucks that have their containers picked up by an ASC. On the pier-side, containers are retrieved by straddle carriers or automated guided vehicles (AGV; for fully automated terminals) and brought to the end of a stack. The main differences between conventional and automated container terminal configurations are that the latter reduces horizontal ground movements and removes vehicles from the stacking areas, enabling a higher stacking density.
Areas close to container terminals tend to have a high concentration of activities linked to freight distribution, such as distribution centers, empty container storage depots, trucking companies, and large retailers. This is commonly associated with high congestion levels around the port terminal facilities. To deal with the issue, the design of several container terminals has been modified to include coordination between on-dock rail facilities and satellite terminals as well as container depots. The goal is to transfer a part of the footprint to another less constrained location.
7. Terminal Capacity Use and Optimization
Terminal equipment is combined to form an integrated container terminal system. The total terminal capacity is determined by the interaction between three levels, which are the quay, the yard, and the gate system:
- Ship or quay-related operational challenges include the berth allocation problem (BAP), the vessel stowage planning problem, and the quay crane assignment/scheduling problem (QCAP). In most cases, berth and quay crane planning are combined in the integrated berth allocation and quay crane assignment problem (BACAP).
- The yard allocation problem (YAP) involves the design of the stacking area (in terms of stacking height and slot capacity) or the optimization of container storage and stacking operations as a function of container type (reefer, dry, liquid), container flow (import, export, transshipment, empties) and dwell time characteristics. Yard-related issues also deal with intra-terminal transport, such as the transport between the quayside and the stacking area and the intra-terminal reshuffling of containers. Here, the optimization of yard operations usually involves an integrated approach, such as by simultaneously determining the yard crane schedules and the vehicle parking positions.
- Gate optimization deals with the connectivity of terminals to landside transportation modes, such as rail transport, inland barges, and trucking. Typical operational challenges in this field include the truck gate process optimization problem, gate appointment systems, the equipment assignment problem, and the modal separation on a terminal in space and time.
The optimal container terminal design is rectangular, but the relationship between water, yard, and gate capacity varies according to the terminal function. Gateway terminals tend to be more square-shaped (more yard space), while transshipment hubs tend to be elongated rectangles (more berth space). Terminal optimization is about optimizing the quay, yard, and gate operations individually and finding an optimal balance between the three capacity dimensions. For example, terminal operators can find a better balance between quay and yard capacity by focusing on hardware investments (infrastructure, equipment), software (optimizations using IT solutions), and orgware (for example, through pricing incentives).
In the past decades, terminal operators have developed a more integrated view on container terminal optimization, often relying on simulation approaches to analyze terminal operations from a system-based perspective combining BAP/QCAP/BACAP with YAP. Discrete-event simulation remains one of the most popular techniques in terminal operations modeling. Other techniques have been used, such as agent-based modeling, network-based modeling, simulation-based education, and web-based simulation. These optimization techniques are incorporated in terminal design applications and Terminal Operating Systems (TOS). Artificial intelligence (AI) and advanced machine learning have also found their way to terminal optimization.
- Chapter 3.1 Terminals and Terminal Operators
- Chapter 3.2 Terminal Concessions and Land Leases
- Chapter 3.7 Dock Labor
- Chapter 3.8 Terminal Automation
- Chapter 8.1 Cruise Ports
- Chapter 8.2 Break-Bulk
- Further references to be added