When it comes to container port operations, two types of cranes dominate the conversation: the RTG crane (Rubber Tyred Gantry Crane) and the STS crane (Ship-to-Shore Crane). Both are essential to modern container terminals, yet they serve fundamentally different roles. Whether you are a port planner, equipment procurement specialist, or logistics professional, understanding the differences between RTG cranes and STS cranes is critical for optimizing operational efficiency and making informed investment decisions.
This comprehensive guide breaks down everything you need to know about RTG cranes vs STS cranes — from technical specifications and working principles to applications, advantages, and how to choose the right equipment for your port.
What Is an RTG Crane?
An RTG crane, short for Rubber Tyred Gantry Crane, is a mobile gantry crane mounted on rubber tyres, specifically designed for container stacking and yard management operations within a terminal’s storage yard. Unlike rail-mounted alternatives, the RTG crane moves freely across the yard without fixed infrastructure, making it one of the most flexible and widely deployed pieces of equipment in container terminals worldwide.
How an RTG Crane Works
The RTG crane straddles a row of containers and uses a spreader attached to its hoisting mechanism to lift, move, and stack containers within defined yard blocks. The crane operator — seated in a cab or controlling remotely — drives the RTG crane along the yard lane, positioning it precisely over target containers.
Key Features of RTG Cranes
- Mobility: Moves on rubber tyres, requiring no rail installation
- Stacking height: Typically handles 5–6 container tiers; newer models reach 7 tiers
- Span width: Usually covers 6 container rows plus a truck lane
- Power options: Diesel engine, diesel-electric hybrid, or fully electric (e-RTG)
- Automation-ready: Supports remote operation and fully automated (ARTG) configurations
- Deployment flexibility: Can be relocated as yard layouts change
RTG cranes are the backbone of yard operations at medium to large container terminals. Their ability to be redeployed without civil engineering works makes them especially valuable for ports with fluctuating throughput or evolving yard layouts.
What Is an STS Crane?
An STS crane, short for Ship-to-Shore Crane (also called a quay crane or container crane), is a large fixed structure installed along the quayside to load and unload containers directly between vessels and the terminal. STS cranes are among the largest pieces of machinery in the world and are the primary indicator of a port’s vessel-handling capacity and operational throughput.
How an STS Crane Works
The STS crane runs along rails fixed to the quay apron, parallel to the berth. Its boom extends outward over the ship, and a trolley travels along the boom carrying a spreader that lifts containers from vessel holds or deck. The crane then swings the container back over the quay, where it is transferred to yard tractors or automated guided vehicles (AGVs) for delivery to the storage yard.
Key Features of STS Cranes
- Outreach: Boom extends 50–70+ meters to cover the full beam of Ultra Large Container Vessels (ULCVs)
- Lifting height: Up to 40+ meters above rail, accommodating vessels stacking 18–25 container tiers
- Lifting capacity: Typically 40–65 tonnes; twin-lift spreaders can handle two 20-foot containers simultaneously
- Productivity: Advanced STS cranes achieve 30+ gross moves per hour (GMPH)
- Drive system: Entirely electric-powered, often equipped with energy regeneration systems
- Rail-mounted: Fixed to quayside rail tracks; cannot be relocated without major reconstruction
STS cranes define a port’s ability to service the world’s largest vessels efficiently. As mega-ships continue to grow in size, ports compete aggressively to upgrade their STS cranes and attract premium liner service calls.
RTG Crane vs STS Crane: Key Differences at a GlanceDimensionRTG CraneSTS CraneFull NameRubber Tyred Gantry CraneShip-to-Shore CranePrimary FunctionYard stacking & container retrievalVessel loading & unloadingMobilityFree-moving on rubber tyresRail-fixed along quaysideLifting Height5–7 container tiers18–25+ container tiersOutreachN/A (yard operation only)50–70+ metersProductivityModerate (yard management)Very high (30+ GMPH)Power SourceDiesel or electricElectric onlyAutomation LevelSemi-auto to fully automatedSemi-auto to fully automatedFootprintFlexible, low infrastructureLarge, requires fixed foundationsMaintenance CostModerateHigh (complex structure)Best ForMid-to-large terminal yardsLarge & mega container ports
Detailed Comparison: Technical SpecificationsStructural Design
The RTG crane features a portal frame supported on four corner bogies, each fitted with multiple rubber tyres. This design keeps ground bearing pressure manageable while enabling full mobility. The gantry spans across a defined number of container rows and travels longitudinally along a yard block.
The STS crane is an entirely different structural proposition. Its towering legs straddle the quay apron and are connected by a cross-beam from which the boom extends seaward. The sheer scale of an STS crane — often standing over 80 meters tall with the boom raised — demands reinforced quay foundations and sophisticated structural engineering.
Spreader Technology
Both RTG cranes and STS cranes use automatic spreaders to grip ISO containers at their corner castings. RTG cranes typically use single-lift spreaders adjustable between 20-foot and 40-foot lengths. STS cranes increasingly feature tandem twin-lift spreaders capable of simultaneously handling two 20-foot containers, effectively doubling theoretical throughput.
Automation Capabilities
Both crane types are increasingly deployed in automated configurations:
- ARTG (Automated RTG): Uses laser sensors, machine vision, and automated control systems to perform stacking operations without a human operator in the cab. Deployed at major automated terminals such as Rotterdam’s Maasvlakte II and Shanghai Yangshan Phase IV.
- Semi-automated STS cranes: Automate the horizontal trolley travel and container positioning over the vessel, while a remote operator handles the final lowering and twist-lock operations for safety.
Application ScenariosWhen to Choose an RTG Crane
RTG cranes are the optimal choice when:
- You operate a mid-sized container terminal where yard layout flexibility is essential
- Your port experiences seasonal throughput fluctuations requiring adaptable yard capacity
- You are developing an inland container depot (ICD) or dry port with limited civil infrastructure budget
- You need a cost-effective path to automation through phased ARTG deployment
- Your terminal requires frequent yard block reconfiguration due to changing trade patterns
When to Choose an STS Crane
STS cranes are essential when:
- Your port serves large container vessels (Post-Panamax, New Panamax, or ULCV class)
- You operate a major international hub or transshipment terminal where vessel turnaround time is critical
- Your business case depends on attracting premium mainline shipping services
- You are developing a deep-water berth designed for next-generation mega-ships
- Your terminal’s competitive advantage relies on best-in-class quayside productivity
The Integrated Terminal: RTG and STS Working Together
In practice, a well-functioning container terminal always deploys both RTG cranes and STS cranes as complementary systems. The STS crane handles the time-critical ship-to-shore exchange, while RTG cranes manage the subsequent yard storage, sorting, and truck delivery operations. Optimizing the handoff between STS cranes and RTG cranes — through effective terminal operating system (TOS) integration — is key to maximizing overall terminal productivity.
Advantages and DisadvantagesRTG Crane: Pros and Cons
Advantages:
- High operational flexibility; no fixed rail infrastructure required
- Lower initial civil works investment compared to rail-mounted alternatives
- Easily relocated as terminal needs evolve
- Wide range of automation options available
- Suitable for phased electrification and decarbonization upgrades
Disadvantages:
- Lower precision than rail-mounted cranes in fully automated configurations
- Rubber tyres require regular maintenance and replacement
- Diesel-powered RTGs contribute to terminal carbon emissions (mitigated by e-RTG conversion)
- Cannot perform ship-side operations
STS Crane: Pros and Cons
Advantages:
- Unmatched productivity for vessel loading/unloading
- Capable of servicing the world’s largest container ships
- Fully electric operation supports green port initiatives
- Long operational lifespan (30+ years with proper maintenance)
- Critical asset for attracting major shipping line services
Disadvantages:
- Very high capital investment and complex installation
- Fixed to quayside; cannot be relocated without major reconstruction
- Requires reinforced quay structures and deep-water berths
- Long procurement and delivery lead times (typically 18–30 months)
Technology TrendsRTG Crane Innovations
The electrification of RTG cranes (e-RTG) is the single most significant trend in yard equipment. Converting diesel RTGs to electric power — via high-voltage cable reels or busbar systems — reduces fuel costs by up to 80% and eliminates local exhaust emissions. Leading manufacturers including Konecranes, Liebherr, and ZPMC now offer fully electric RTG crane models as standard products.
Meanwhile, automated RTG (ARTG) deployments are accelerating globally. Advancements in LiDAR-based positioning, AI-powered scheduling algorithms, and remote monitoring systems are making ARTG technology increasingly accessible even for terminals outside the top-tier automated terminal category.
STS Crane Innovations
STS crane development is being driven primarily by the relentless growth of vessel sizes. Modern Post-Panamax and Super Post-Panamax STS cranes now offer outreaches exceeding 70 meters to cover vessels with 24+ container rows across their beam. Tandem twin-lift technology has become standard on new STS crane orders at major terminals, and AI-assisted anti-sway systems are significantly reducing cycle times and improving safety.
Energy efficiency is also a priority: regenerative drive systems on STS cranes recover energy during container lowering cycles, reducing overall power consumption by 20–30%.
How to Choose: RTG Crane or STS Crane?
The question of RTG crane vs STS crane is ultimately not an either/or decision — it is a question of system configuration. Here is a practical decision framework:
- Define your vessel profile. If your terminal targets mainline services with vessels above 8,000 TEU, STS cranes are non-negotiable.
- Assess your annual throughput target. Terminals above 500,000 TEU/year typically require both STS cranes and RTG cranes operating in a coordinated system.
- Evaluate your yard area and layout stability. Flexible, evolving yards favor RTG cranes; stable, high-density automated yards may favor RMG cranes as an alternative.
- Consider your automation roadmap. Both RTG and STS cranes offer automation upgrade paths — align your procurement with your 10-year automation strategy.
- Factor in total cost of ownership (TCO). Beyond purchase price, account for civil works, energy costs, maintenance, and operational staffing across the equipment lifecycle.
FAQ
Q: What is the difference between an RTG crane and an RMG crane?A: An RTG crane (Rubber Tyred Gantry) moves on rubber tyres without fixed rails, offering high flexibility. An RMG crane (Rail Mounted Gantry) runs on rails embedded in the yard pavement, providing higher positioning accuracy and better suitability for full automation. Both are yard equipment — the choice depends on the terminal’s automation ambition and infrastructure investment appetite.
Q: How many RTG cranes does a terminal typically need per STS crane?A: A common rule of thumb is 3–5 RTG cranes per STS crane, depending on yard depth, dwell time, and the balance between import, export, and transshipment cargo. High-volume transshipment terminals with short dwell times may need fewer RTGs per STS crane than import-heavy terminals with longer storage cycles.
Q: Can an RTG crane replace an STS crane?A: No. RTG cranes and STS cranes perform entirely different functions and operate in different zones of the terminal. An RTG crane has no capability to reach over a vessel, and an STS crane cannot manage yard stacking. They are complementary, not interchangeable.
Q: What is the lifespan of an RTG crane vs an STS crane?A: Both types of equipment have operational lifespans of 20–30+ years with proper maintenance. STS cranes, due to their structural complexity and higher capital cost, are typically maintained and upgraded over longer periods. RTG cranes may be refurbished or converted to electric drive mid-life to extend their useful service.
Q: Which crane type is more environmentally friendly?A: STS cranes are inherently electric-powered and generally more energy-efficient on a per-move basis. RTG cranes vary — diesel-powered RTGs have a significant carbon footprint, while e-RTG cranes are broadly comparable to STS cranes in terms of emissions. The industry trend is clearly toward full electrification of both crane types.
