RTG vs RMG Crane: Which Container Yard Stacking Solution Fits Your Terminal?
Introduction
Two crane technologies dominate container yard stacking worldwide. Rubber-Tired Gantry cranes (RTG) run on pneumatic tires. Rail-Mounted Gantry cranes (RMG) run on fixed steel rails. Both stack containers. Both serve the same fundamental purpose. But they make completely different promises to the terminal operator.
The RTG promises flexibility. Move the crane between yard blocks. Reposition when traffic patterns change. Expand the terminal without demolishing and rebuilding fixed infrastructure.
The RMG promises precision and automation. Fixed rails mean precise positioning every time. Rail-mounted systems integrate more cleanly with fully automated terminal control. Energy efficiency is higher because regenerative braking returns power to the grid reliably.
Choosing between them is one of the most significant capital decisions a container terminal makes. The wrong choice creates operational constraints that persist for 20 to 30 years.
This guide compares RTG and RMG cranes across seven dimensions. It provides a decision framework based on terminal type, throughput level, and automation ambition.
Part 1: Structural and Operational Differences
RTG — Rubber-Tired Gantry
An RTG is a mobile gantry crane mounted on pneumatic rubber tires. It straddles a row of container stacks and travels perpendicular to the stack rows to position over the correct bay. Its tires can rotate 90 degrees to allow the crane to travel parallel to the stack rows — moving from one row block to another.
Key structural features:
Span: typically 6+1 to 8+1 container rows wide (6 or 8 container rows plus one truck lane).
Stack height: typically 1-over-4 to 1-over-6 (one container over 4 to 6 stacked containers).
Lifting capacity under spreader: 40 to 65 tonnes for standard RTGs.
Power: diesel generator (100 to 600 kW), diesel-hybrid, or fully electric (cable reel or busbar).
Travel speed: 130 to 180 m/min along rows.
Steer capability: 90-degree tire rotation allows block-to-block transfer.
RMG — Rail-Mounted Gantry
An RMG is a gantry crane that runs on fixed steel rails embedded in the yard surface. The rails define the crane’s travel path permanently. The crane cannot be repositioned without excavating and relaying the rails.
Key structural features:
Span: typically 6+1 to 10+1 container rows wide. Larger spans are practical with RMG because the rails provide rigid lateral support.
Stack height: same as RTG — typically 1-over-5 to 1-over-6.
Lifting capacity: 40 to 65 tonnes standard. Higher capacities available.
Power: almost always electrically powered via conductor rail or overhead catenary. No onboard generator required.
Travel speed: 180 to 240 m/min — typically faster than RTG due to the rigid rail guidance.
Steer capability: none. The crane follows the rails only.
Part 2: Seven-Dimension Comparison
Dimension 1: Flexibility and Repositionability
RTG: can be driven between yard blocks under its own power. Repositioning a crane from Block A to Block C takes minutes. When terminal layout changes — new berths, reconfigured yard blocks — the RTG fleet adapts without infrastructure investment.
RMG: permanently fixed to its rails. Repositioning requires: excavating the rail foundations, relaying the rails at the new position, reconnecting the power supply, and recommissioning the crane. Cost: $500,000 to $2,000,000 per crane relocation. Time: weeks to months.
Winner for flexibility: RTG — decisively.
Dimension 2: Yard Density and Stacking Height
RTG: the tire mechanism requires clearance space at yard block ends for the 90-degree turn maneuver. End aisles of 5 to 8 metres are required. This reduces the usable stacking area per unit of yard footprint.
RMG: no tire turning requirement. Yard blocks can be longer relative to the end aisle width. RMG systems typically achieve 5 to 15% higher container storage density per hectare of yard than equivalent RTG systems.
Winner for yard density: RMG — marginal advantage.
Dimension 3: Automation Compatibility
RTG: the tire-based travel system requires GNSS positioning (GPS/GNSS with differential corrections) for automated operation. Position accuracy with RTK corrections: ±10 to ±20mm — adequate for automated stacking but less precise than rail-based systems. Automation retrofit cost is significant: positioning systems, camera systems, control system replacement.
RMG: rail-guided travel provides inherent repeatability. The crane’s longitudinal position is determined by absolute encoders on the rail wheels — no GNSS required. Positioning accuracy: ±2 to ±5mm. RMG cranes integrate more cleanly and at lower cost into fully automated terminal control systems.
Winner for automation compatibility: RMG — significant advantage for high-automation terminals.
Dimension 4: Energy Efficiency
RTG (diesel): fuel consumption 12 to 18 litres per operating hour. CO₂ emissions: 32 to 48 kg per operating hour. Highest operating cost of any container yard crane option.
RTG (electric, cable reel or busbar): energy consumption 15 to 25 kWh per operating hour. CO₂ at EU grid intensity: 3.5 to 5.8 kg per operating hour.
RMG (electric, conductor rail): energy consumption 12 to 20 kWh per operating hour. Regenerative braking returns 15 to 25% of lifting energy to the grid. Net consumption after regeneration: 9 to 17 kWh per operating hour. CO₂ at EU grid intensity: 2.1 to 3.9 kg per operating hour.
Winner for energy efficiency: Electric RMG — lower consumption and better regeneration efficiency than electric RTG.
Dimension 5: Infrastructure Investment
RTG: the primary infrastructure requirement is a flat, strong yard surface — typically reinforced concrete or heavy-duty asphalt. No embedded rail. No fixed power distribution along rail lines. Infrastructure cost per crane position: $50,000 to $200,000 (yard surface only).
RMG: requires embedded rail foundations along the full travel length of every crane. Rail foundation cost: $800 to $1,500 per running metre (both rails combined). For a 400-metre block with 4 RMG cranes: $640,000 to $1,200,000 in rail foundations alone — before the cranes themselves.
Winner for infrastructure cost: RTG — significantly lower upfront infrastructure investment.
Dimension 6: Throughput Performance
RTG cycle time for a standard pickup-travel-deposit cycle: 90 to 130 seconds.
Moves per hour: 25 to 35 for a skilled operator; 28 to 32 for automated RTG.
RMG cycle time: 75 to 110 seconds (faster travel speed from rigid rail guidance).
Moves per hour: 28 to 38 for automated RMG with anti-sway.
Winner for throughput: RMG — marginal advantage from faster travel speed and better positioning repeatability.
Dimension 7: Total Cost of Ownership Over 20 Years
RTG (diesel, manual operation): high fuel cost + operator cost dominates TCO.
RTG (electric, semi-automated): lower energy cost. Moderate operator cost (4 to 6 cranes per operator position).
RMG (electric, fully automated): highest capital cost (crane + rail infrastructure). Near-zero operator cost. Lowest energy cost. Best TCO at high throughput volumes.
The breakeven point where RMG TCO drops below RTG TCO: typically 400,000 to 600,000 moves per year per terminal block. Below this throughput, the higher infrastructure and capital cost of RMG is not recovered through lower operating cost.
Part 3: Decision Framework
Terminal Type 1: Greenfield High-Volume Automated Terminal
Throughput: above 600,000 TEU per year per terminal block.
Automation target: Level 3 to Level 4 (fully automated).
Long-term layout commitment: fixed yard block layout for 20+ years.
Recommendation: RMG. The automation compatibility, throughput performance, and energy efficiency advantages justify the higher infrastructure cost at this volume. All major new automated terminals built since 2015 use RMG or similar rail-guided systems.
Terminal Type 2: Existing Terminal Expansion or Upgrade
Throughput: 200,000 to 600,000 TEU per year per block.
Automation target: semi-automated (Level 2) initially.
Layout flexibility: yard block layout may change as the terminal evolves.
Recommendation: Electric RTG with automation upgrade path. The flexibility to reposition cranes as the yard evolves outweighs the efficiency advantage of RMG at this throughput level. Specify electric RTG (busbar or cable reel) from the outset to avoid diesel-to-electric conversion costs later.
Terminal Type 3: Smaller Regional or Feeder Terminal
Throughput: below 200,000 TEU per year.
Automation target: primarily manual with remote operation consideration.
Capital constraint: limited infrastructure budget.
Recommendation: RTG (diesel-hybrid or electric). The infrastructure saving over RMG is decisive at this scale. Diesel-hybrid provides lower operating cost than pure diesel while avoiding the busbar infrastructure investment.
Terminal Type 4: Inland Container Depot or Rail Terminal
Throughput: variable. Often lower than port terminals.
Automation target: varies widely.
Power supply: often limited — adding large electrical infrastructure may not be feasible.
Recommendation: RTG. The rail terminal’s layout typically changes seasonally and annually. RTG flexibility is essential. For locations where grid power is limited: diesel-hybrid RTG provides the best balance of fuel efficiency and independence from fixed electrical infrastructure.
Part 4: Hybrid and Emerging Options
E-RTG (Electrified RTG)
An E-RTG is a diesel RTG converted to electric operation through addition of a cable reel or busbar power pickup. The diesel generator remains as backup. The crane runs on grid power during normal operation — saving 80 to 90% of fuel costs.
E-RTG conversion is the most common upgrade path for existing diesel RTG fleets. Cost per crane: $150,000 to $350,000 for the electrification upgrade. Payback through fuel savings: 2 to 4 years at current diesel prices.
Battery RTG
A fully battery-electric RTG with no diesel backup and no cable or busbar connection. The crane charges during shift breaks at a dedicated charging station.
Battery RTG advantages: no cable management, no busbar infrastructure, full yard mobility maintained. Battery RTG disadvantages: battery capacity limits shift length, charging infrastructure required, battery replacement cost after 8 to 14 years.
Konecranes E-Hybrid RTG (2025): charges from a 60 kW grid connection — far less than the 400 kW required for direct electric operation. This dramatically reduces the electrical infrastructure investment while achieving near-electric operating economics.
Frequently Asked Questions
Q: Can an RTG terminal be converted to RMG in the future?
A: Yes, but at substantial cost. Conversion requires: excavating the existing yard surface to install rail foundations, installing new rail infrastructure, purchasing new RMG cranes (or significantly modifying existing RTGs), and installing fixed electrical power distribution. The total conversion cost typically exceeds $5M to $15M per yard block. For terminals planning a long-term move to full automation, designing the yard block dimensions and surface specifications for future RMG compatibility from the start reduces the eventual conversion cost.
Q: Which system has a longer service life?
A: Both RTG and RMG cranes have design service lives of 20 to 25 years for the crane structure. The rail infrastructure for RMG has a service life of 25 to 40 years with proper maintenance. RTG tires require replacement every 18 to 36 months depending on operating intensity — an ongoing maintenance cost with no equivalent in RMG systems. Rail maintenance (grinding, clip replacement, joint inspection) is the RMG equivalent but is typically less frequent and lower unit cost than tire replacement.
Q: Is an RMG crane more expensive than an RTG?
A: The crane itself (excluding infrastructure) is similar in price: $1.5M to $4.5M for both types at standard capacities. The infrastructure difference is where RMG becomes significantly more expensive: rail foundations, fixed electrical distribution, and any required ground leveling for the rail alignment add $800,000 to $2,500,000 per crane position in infrastructure cost.