Fact-checked by Grok 2 weeks ago

Slow steaming

Slow steaming is a operational strategy in which ships intentionally reduce their cruising speeds below conventional levels to minimize fuel consumption and , typically operating container vessels at 18-20 knots or less compared to the standard 22-25 knots. This practice emerged prominently in the shipping industry during the late 2000s, initially as a response to surging bunker fuel prices following the 2008 global financial crisis, with major carriers like adopting it to cut operational costs amid overcapacity and reduced demand. By 2010, it had become an industry-wide trend, with speeds dropping to as low as 14-18 knots in some cases, and it persisted into the due to ongoing economic pressures and growing environmental regulations. The primary benefits of slow steaming include substantial savings—often 20-30% for a 10% speed reduction—directly translating to lower voyage costs and reduced emissions by a similar margin per moved, making it a cost-effective measure for compliance with international standards like those from the . Additionally, operating engines at lower loads can extend machinery lifespan by reducing , while the strategy has contributed to broader decarbonization efforts in shipping without requiring major technological overhauls. However, slow steaming presents challenges, including extended transit times that disrupt just-in-time supply chains, potentially increasing holding costs for shippers and leading to delays in flows. It can also strain engines not originally designed for prolonged low-speed , risking higher needs or reduced in certain vessel types, though modern adaptations like arrival systems help mitigate scheduling issues. As of 2025, with bunker fuel prices relatively stable around $600-700 per ton in recent months and stricter emissions targets under the IMO's net-zero goal by 2050, slow steaming remains a key tactic alongside innovations like alternative fuels; non-governmental organizations continue to advocate for its to enhance decarbonization, though its long-term viability depends on balancing economic and environmental priorities.

Fundamentals

Definition

Slow steaming is the intentional reduction of a ship's operating speed below its design or maximum rated speed to achieve and lower emissions, typically involving a 10-20% decrease, such as from 25 knots to 18-20 knots for large container vessels. This practice emerged as a response to rising prices around 2007-2008, enabling operators to optimize costs amid volatile conditions. The strategy is primarily applied to ocean-going cargo vessels, including container ships, tankers, and bulk carriers, where sustained lower speeds can yield substantial fuel savings without compromising safety when properly managed. It differs from incidental speed variations caused by weather or routing, as slow steaming constitutes a deliberate, ongoing operational policy rather than reactive adjustments. Key terms delineate the degree of speed reduction: "slow steaming" generally refers to operations around 21 knots, "extra slow steaming" to about 18 knots, and "super slow steaming" to 15 knots or below, often requiring engine modifications for loads under 50% of maximum continuous rating. A prominent example is Line's 2009 adoption of slow steaming at 18 knots across its fleet, including Emma Maersk-class ships, which demonstrated the feasibility of sustained reductions for efficiency gains.

Physical Principles

Slow steaming leverages fundamental hydrodynamic principles to achieve significant fuel savings by reducing vessel speed. The total resistance encountered by a ship in water comprises frictional drag, which dominates at lower speeds and is proportional to the square of the velocity (R_F ∝ V²), and wave-making resistance, which increases more rapidly at higher speeds. Since propulsive power is the product of resistance and velocity (P = R × V), the required power scales approximately with the cube of the speed for many vessel types (P ∝ V³), particularly at low Froude numbers where wave effects are minimal. For ships operating in typical service speeds, this exponent can range from 3.2 to 3.8, as observed in tankers and bulk carriers. This cubic relationship implies substantial gains from modest speed reductions; for instance, a 10% decrease in speed (from V to 0.9V) reduces power demand by about 27% ((0.9)³ ≈ 0.729), directly translating to lower consumption assuming constant specific fuel consumption (SFC). The equation can be expressed as: P \propto k \cdot V^n where n \approx 3 for low-speed regimes, and k incorporates hull form and environmental factors. This principle holds in calm water but may deviate in heavy weather, where additional alters the exponent. Propulsion efficiency further influences slow steaming outcomes. Propellers are designed for optimal open-water (η_O ≈ 0.55–0.70) at the vessel's speed, where advance and align to maximize per input. At reduced speeds, the propeller operates off-design, experiencing a drop in due to risks or suboptimal slip, potentially by 5–10% for reductions up to 20%. However, the dominant cubic savings typically outweigh these losses for moderate slow steaming (10–20% speed cuts), maintaining net hydrodynamic benefits. Diesel engines in applications exhibit their lowest SFC—typically 155–225 g/kWh—at partial loads of 70–85% of maximum continuous rating (MCR), where efficiency peaks and thermal losses are minimized. Slow steaming aligns engine operation within this range for many vessels, as speeds often correspond to 70–80% load; further reductions to 50–60% may increase SFC by 2–5% due to poorer , but overall fuel use still declines owing to the power-speed . Low-load options can mitigate this, optimizing SFC for prolonged sub- operation.

Historical Development

Origins in the 2000s

The practice of slow steaming emerged in the late as container shipping lines grappled with escalating bunker fuel prices, which surged to peaks exceeding $700 per metric ton in amid oil market volatility and surging global demand. This price escalation, representing an over 800% increase from the levels, placed immense pressure on operational costs, prompting initial experiments with speed reductions to curb fuel consumption. First documented trials occurred in among shippers on major trade routes, driven by the need to mitigate these rising expenses during a period of economic uncertainty. Major carriers, including , pioneered broader implementation starting in 2007, with systematic adoption accelerating in 2009 as fuel costs accounted for 50-60% of total operating expenses. , for instance, reduced average speeds on Asia-Europe routes from around 25 knots to 20 knots, extending voyage times but achieving substantial savings without compromising engine integrity after initial testing. These early efforts were primarily motivated by cost-saving imperatives rather than environmental goals, as lines sought to maintain profitability amid softening freight rates. The 2008-2009 global financial crisis further amplified slow steaming's uptake, as declining volumes and overcapacity exacerbated the cost burden, leading to widespread voluntary speed reductions across the industry. By late 2009, practices like "super slow steaming" at speeds below 20 knots became common, marking a shift from trials to a strategic operational norm for major operators.

Widespread Adoption

Slow steaming transitioned from an initial response to economic pressures in the late 2000s to a widespread industry practice throughout the , particularly among container shipping lines. By 2011, major operators had adopted reduced speeds across significant portions of their fleets, absorbing excess operational capacity through consistent speed reductions on key routes. This growth was exemplified by A.P. Moller-, which implemented slow steaming across its entire container fleet starting in 2009 and achieved full operational integration by 2010, resulting in average engine loads dropping to below 40%. The practice subsequently extended to other vessel types, with tankers and bulk carriers increasingly adopting slow steaming by 2012 amid persistent high fuel costs and overcapacity, leading to observable speed reductions in these segments. Additionally, super slow steaming trials, involving speeds below 18 knots, were conducted by and engine manufacturers between 2011 and 2013 to assess engine reliability at ultra-low loads, confirming minimal risk of damage and paving the way for broader application. The International Maritime Organization's Energy Efficiency Design Index (EEDI), which entered into force on January 1, 2013, further influenced this expansion by mandating improved for new ships, incentivizing operational measures like speed reduction. Following a period of variable adoption in the late , slow steaming resurged prominently during the from 2020 to 2022, as global disruptions, congestions, and excess capacity prompted carriers to curtail speeds to balance service levels and control costs. This revival aligned with broader decarbonization objectives, as reduced speeds directly lowered consumption and emissions, supporting with emerging environmental targets. By 2023, industry analyses indicated high levels of integration, with average speeds falling to 13.8 knots—a 4% decline from prior years—and slow steaming contributing to a 4.6% reduction in overall fleet between 2019 and 2023, particularly in segments. In 2024, average speeds rose slightly to 14.8 knots amid recovering , before stabilizing at 14.0 knots in early 2025, indicating moderated but ongoing use of slow steaming. Adoption rates varied regionally, with higher prevalence on densely trafficked Asia-Europe routes, where substantial trade volumes facilitated longer transit times without severely impacting supply chains. These corridors, accounting for a large share of global containerized trade, saw consistent slow steaming implementation from the early onward, enabling carriers to optimize fuel use amid fluctuating demand.

Operational Implementation

Strategies for Speed Reduction

Slow steaming strategies encompass both voluntary and regulated approaches to reduce vessel speeds in maritime operations. Voluntary slow steaming is primarily market-driven, where operators reduce speeds to cut fuel costs during periods of low demand or high fuel prices, as exemplified by Maersk's implementation of super slow steaming at around 14 knots on major routes. In contrast, regulated slow steaming involves mandatory measures enforced through international or regional policies to improve carbon intensity, such as compliance with the Carbon Intensity Indicator (CII) regulation, which requires annual improvements in carbon intensity and may necessitate gradual speed reductions, such as a total of about 2 knots from 2023 to 2030, to maintain minimum rating thresholds. Voluntary incentives, such as those in U.S. ports offering 15-25% dockage discounts for high compliance rates in speed reductions below 12 knots, encourage participation in programs like the Vessel Speed Reduction initiative. As of 2025, slow steaming remains a primary operational measure for CII compliance amid ongoing IMO decarbonization goals. Voyage planning plays a central role in maintaining consistent low speeds while minimizing disruptions. Operators utilize routing software to optimize routes, accounting for currents, winds, and forecasts to sustain reduced speeds without excessive deviations, thereby enhancing . A key tactic is just-in-time () arrival, where vessels adjust speeds—often slowing from 19 knots to 12 knots—to synchronize with berth availability, pilot boarding, and services, avoiding idling at anchorages that can account for 5-10% of global ship time and reducing use by up to 23% on routes like Bremerhaven to . This approach relies on frequent estimated time of arrival () updates, such as 12-hour notices to ports, which can cut CO2 emissions by 4% through better coordination. Fleet management requires adjustments to accommodate longer transit times inherent in slow steaming. On trans-Pacific routes, for instance, speed reductions can extend round-trip durations by 10-20%, adding 4-7 days per voyage and necessitating scheduling revisions to maintain service frequency, often through inventory buffering by shippers to offset delays in cargo delivery. Simulation studies of bulk carrier fleets show that a 2-knot reduction (slow steaming) decreases annual voyages and cargo throughput to about 99.9% of baseline levels, while a 4-knot cut (ultra-slow steaming) drops it to 93%, requiring an additional vessel to preserve capacity. Monitoring tools ensure adherence to speed protocols in . The Automatic Identification System (AIS), mandatory for ships over 500 gross tons, transmits speed-over-ground data every 2-10 seconds, enabling regulators and operators to track compliance remotely via satellite or terrestrial networks, as utilized in programs like the Vessel Speed Reduction initiative. Complementing this, crew training on low-speed protocols is integrated into Ship Energy Efficiency Management Plans (SEEMP) and energy efficiency operational indicator (EEOI) programs, focusing on safe engine handling at derated loads, voyage monitoring, and protocol adherence to prevent operational risks during reduced speeds.

Engine and Propulsion Adjustments

Engine derating involves reducing the maximum continuous rating (MCR) of marine engines by 10-15% to enable safe slow steaming operations, typically achieved through software tuning or hardware modifications such as cut-outs or deactivation. These adjustments optimize the engine's at reduced speeds, preventing overload conditions by improving the power-to-maximum (Pmax/MEP) ratio and ensuring compatibility with performance and limits. For instance, slow steaming kits can be retrofitted to existing engines, allowing a top speed reduction while maintaining operational reliability. Propeller retrofits are essential for slow steaming, as fixed-pitch propellers (FPPs) exhibit reduced below their design speed due to suboptimal hydrodynamic loading and risks. Solutions include upgrading to ducted s, such as high-performance nozzles, which enhance and for heavily loaded conditions at lower speeds, potentially improving overall by up to 15%. Alternatively, replacing FPPs with controllable-pitch propellers (CPPs) allows precise pitch adjustments to match varying loads, maximizing across partial load ranges common in slow steaming. Adjustments to auxiliary systems ensure optimal and component longevity at partial loads during slow steaming. Fuel pumps and injectors require to maintain fuel at 12-13 cSt for proper , as lower loads can impair spray penetration and lead to incomplete . Turbochargers, optimized for 70-85% loads, may need upgrades like selective cut-out of units to sustain scavenge air pressure at 50-60% loads, preventing and drops. systems benefit from pulse lubrication techniques, which reduce cylinder consumption by 20-40% while addressing low-RPM hydrodynamic challenges, and cooling optimizations—such as maintaining jacket water at 85-95°C and low-temperature water at 36°C—minimize and . Wärtsilä's guidelines for 2-stroke engines exemplify these adjustments through their Slow Steaming Upgrade Kit, which enables continuous safe operation down to 50% load without significant efficiency loss, achieving (BSFC) reductions of 8-12 g/kWh via modifications and auxiliary tuning. A from a 2009 installation on a 12-cylinder RT-flex96C demonstrated reliable low-load performance with periodic high-load runs to clear deposits, confirming the kit's effectiveness in real-world slow steaming scenarios.

Economic Aspects

Cost Savings

Slow steaming provides direct financial advantages to shipping operators by substantially lowering fuel expenses, which account for 40-60% of total voyage costs in the container shipping sector. The non-linear relationship between vessel speed and consumption—governed by the cubic law of —means that even modest speed reductions yield disproportionate savings. For example, a 10% decrease in speed (e.g., from 24 knots to 21.6 knots) typically results in 20-30% less bunker usage for container ships, as engine demand drops more sharply than speed. This efficiency stems from reduced hydrodynamic resistance and lower engine loads, allowing operators to cut daily fuel burn rates significantly without major retrofits. Practical implementations highlight these benefits, particularly during periods of elevated fuel prices. In 2011 analyses of trans-Pacific routes, reducing speed on a 6,310-nautical-mile voyage from to Long Beach saved approximately $250,000 in fuel costs per trip at prevailing rates, demonstrating the viability for large container . Similarly, major carriers like adopted slow steaming in the late 2000s and early 2010s, achieving fleet-wide fuel reductions of around 9-18% through speed cuts to 18-21 knots, which translated to millions in annual savings across their operations amid $500-700 per fuel prices. These examples underscore how slow steaming enables operators to maintain profitability in overcapacity scenarios by leveraging existing designs for fuel optimization. Beyond fuel, slow steaming enhances operational efficiencies by minimizing engine wear and associated maintenance costs. Lower speeds reduce thermal and mechanical stresses on pistons, liners, and turbochargers, extending overhaul intervals and decreasing unplanned downtime. This leads to lower lubrication and repair expenses. Break-even analysis is essential for determining the economically optimal slow steaming speed, which balances fuel savings against the penalties of extended transit times, such as higher hire or costs. For ships, this equilibrium often occurs at 18-20 knots when bunker fuel prices hover around $500 per , as further reductions yield relative to time-related expenses. Above this price threshold, slower speeds become more attractive; for instance, at $800 per , optimal speeds may drop to 16-18 knots to maximize net savings. Recent estimates for 2023-2025 highlight the ongoing industry-wide impact amid volatile markets, with slow steaming contributing to cost savings on the order of tens of billions of dollars globally. The notes that operational measures like slow steaming and route optimization saved the sector approximately $60 billion in 2023 alone, equivalent to 1.8 million barrels per day of , by enabling sustained speed reductions across major trade lanes. In 2024, geopolitical disruptions like the led to longer routes, yet slow steaming persisted, with speeds averaging 1.5 knots lower than pre-crisis levels, contributing to ongoing savings despite higher overall consumption. These savings are projected to persist through 2025 as carriers prioritize efficiency in response to fluctuating prices and regulatory pressures.

Financial Challenges

One of the primary financial challenges of slow steaming is the extension of transit times, which directly increases operational costs for shipping operators. A 10% reduction in speed, such as from 20 knots to 18 knots, typically results in an approximately 11% increase in voyage duration due to the inverse relationship between speed and time. This prolongation raises hire expenses, as vessels are on hire for additional days, and elevates costs over the extended period. For instance, in scenarios involving significant speed reductions, carriers may incur tens of thousands of dollars in extra and labor costs per voyage, depending on size and route length. Slow steaming also imposes substantial costs on shippers, primarily through elevated holding requirements. Longer transit times necessitate maintaining higher levels of pipeline to buffer against delays, which can increase expenses by 11-37% in cases where savings from are not fully passed on to customers. Additionally, the practice can lead to potential fees at ports if extended voyage durations disrupt scheduled arrivals and exceed free time allowances for handling. These effects are particularly pronounced for time-sensitive or high-value , where each additional day in transit equates to an ad-valorem equivalent of 0.6-2.3% of the 's value. Capacity constraints represent another key economic drawback, as maintaining service frequency under slow steaming often requires deploying more vessels to compensate for reduced speeds. This need for fleet expansion drives up capital expenditures for acquiring or chartering additional ships, potentially offsetting savings and straining financial resources during periods of tight supply. The post-2020 supply crunch, characterized by vessel shortages amid surging demand from recovery, amplified these challenges by limiting operators' ability to scale without incurring hiring rates or delays. In overcapacity scenarios, such as those emerging in , slow steaming further complicates fleet utilization by tying up more at sea. Finally, market volatility undermines the financial viability of slow steaming, as its benefits hinge on favorable freight rates and fuel prices. When spot rates drop below break-even thresholds—such as around $800 per TEU—the additional costs from longer voyages and adjustments can erode profitability, prompting operators to revert to higher speeds. This sensitivity is evident in fluctuating prices and trade volumes, where low-demand periods diminish the strategy's economic rationale despite persistent environmental pressures.

Environmental Impacts

Emission Reductions

Slow steaming significantly reduces from shipping, primarily through decreased fuel consumption linked to lower speeds. A 10% reduction in speed typically lowers CO2 emissions by 19-27%, depending on type and operational conditions, as fuel use scales approximately with the cube of speed. This relationship can be quantified using the formula for CO2 savings: \text{CO}_2 \text{ savings} \approx \left(1 - \left(\frac{V_{\text{reduced}}}{V_{\text{normal}}}\right)^3 \right) \times \text{baseline emissions}, where V_{\text{reduced}} and V_{\text{normal}} represent the reduced and normal speeds, respectively; for a 10% speed cut, this yields about 27% savings before adjustments for factors like added vessels. A 2024 study on post-Panamax container ships showed a 16.89% annual CO2 reduction for a 10% speed decrease while maintaining volume. Widespread adoption of slow steaming since 2010 has contributed to a 10-15% drop in global shipping CO2 emissions, particularly in and sectors during economic downturns and fuel price spikes. This operational strategy has proven effective in curbing the sector's overall without requiring technological overhauls. Emissions of air pollutants such as , , and also decline proportionally to fuel consumption reductions from slow steaming, often by 20-30% for a 10% speed cut. These cuts complement the IMO's 2020 global sulfur cap by further minimizing releases through lower fuel volumes, enhancing compliance and air quality benefits in emission control areas. Tracking these emission reductions is integrated into the International Maritime Organization's (IMO) frameworks, including the Energy Efficiency Design Index (EEDI) for newbuild efficiency baselines and the Ship Energy Efficiency Management Plan (SEEMP) for operational monitoring via indicators like the Energy Efficiency Operational Indicator (EEOI). SEEMP explicitly incorporates slow steaming as a key measure, enabling vessels to document and verify fuel savings and associated CO2 cuts annually.

Other Ecological Effects

Slow steaming contributes to reductions in underwater , which is critical for s that rely on acoustic signals for , , and communication. Studies have shown that slowing commercial vessels to around 11 knots can decrease radiated levels by 6 to 12 across various ship types, including containerships (up to 11.5 reduction) and bulk carriers (about 6 ). These reductions benefit species such as beluga whales, narwhals, and bowhead s in sensitive areas like the , where lower levels help preserve natural soundscapes essential for their behaviors. According to a January 2025 WWF analysis, implementing slow steaming in whale migration corridors could enhance overall welfare by minimizing acoustic disturbances during seasonal movements, with a 10% speed reduction decreasing by about 40%. Another key ecological benefit is the decreased risk of vessel strikes on marine wildlife. For endangered North Atlantic right whales, reducing vessel speeds from 15 knots to 10 knots lowers the probability of fatal collisions by approximately 50%. This effect stems from increased reaction times for both whales and crews, allowing better avoidance during encounters in high-traffic areas. Similar risk reductions, up to 58% in some models, apply to other large whales when speeds are curtailed, supporting population recovery in collision-prone regions. A January 2025 WWF report indicates that speeds below 11.8 knots can reduce whale collision risk by more than 50% in shipping zones. Despite these advantages, slow steaming presents potential ecological drawbacks. To maintain global shipping capacity with slower speeds, fleets may need to expand, potentially requiring 10-20% more vessels, which could offset and collision benefits through increased overall and habitat disruption. Additionally, longer voyage durations from reduced speeds extend the time ships spend at sea, complicating water management and heightening risks of introduction if discharge protocols are not rigorously followed, as prolonged ballast retention can alter organism viability and distribution patterns. Recent research highlights slow steaming's positive contributions to ocean beyond direct and strike effects. A January 2025 WWF report indicates that these practices foster healthier marine ecosystems by alleviating cumulative pressures on migratory , indirectly supporting food webs and integrity in polar and coastal zones.

Advanced Techniques

Smart Steaming

Smart steaming represents an evolution of traditional slow steaming practices, leveraging to enable dynamic, real-time adjustments to speeds based on variables such as patterns, currents, congestion levels, and varying prices. This approach contrasts with static slow steaming, which relies on fixed reduced speeds for the duration of a voyage, by incorporating flexible and deceleration to enhance operational efficiency, reduce idle times, and synchronize with broader demands. Pioneering technologies in smart steaming include the SYNCHRO-NET project, an EU-funded initiative spanning 2015 to 2018 that developed an integrated optimization and simulation eco-network to catalyze slow steaming within synchromodal logistics frameworks. SYNCHRO-NET utilized AI-based algorithms for multi-stakeholder coordination, incorporating analytics to balance costs, emissions, and reliability. Complementary efforts, such as the Global Maritime Energy Efficiency Partnerships (GloMEEP) project led by the , promote operational enhancements like just-in-time arrivals that align with smart steaming by supporting energy-efficient voyage planning and emission reductions. These systems have demonstrated potential for up to 30% additional fuel savings over conventional slow steaming through optimized speed profiles that minimize excess consumption during congestion or suboptimal conditions. Implementation of smart steaming centers on satellite-enabled real-time data sharing among vessels, ports, and operators, coupled with predictive algorithms that forecast optimal speeds for just-in-time arrivals. For example, berth scheduling software integrates voyage simulations to dynamically recalibrate speeds en route, ensuring vessels arrive precisely when berths are available and avoiding fuel-wasting anchorage waits. This process requires robust technological platforms for continuous monitoring and re-planning, fostering greater visibility and automation in global shipping networks. Notable case studies highlight the practical impacts of smart steaming. In SYNCHRO-NET demonstrations, dynamic speed adjustments on multimodal routes reduced CO2 emissions by approximately 25% compared to static profiles, equivalent to avoiding 5 tons of emissions per voyage in simulated scenarios. More recently, Maersk's trials of the AI-powered NavAssist platform, which optimizes routes and speeds using real-time oceanographic data and vessel performance metrics, achieved up to 12% fuel savings on pilot vessels, contributing to overall efficiency gains of 15-20% in integrated operations. By , adoption of AI-driven speed and route optimization technologies has reached 29% among U.S. transport and shipping companies.

Integration with Emerging Technologies

Slow steaming, which involves operating vessels at reduced speeds to conserve fuel, integrates effectively with systems to enhance overall efficiency and emissions reductions. Technologies such as Flettner rotors and sails harness forces to provide auxiliary thrust, amplifying the fuel savings from slow steaming by an additional 10% in propeller power under moderate conditions of 13 knots. Pilots conducted between 2023 and 2025 on bulk carriers, including installations by companies like Norsepower, have demonstrated this synergy, with rotors enabling extra propulsion that complements low-speed operations without requiring significant engine adjustments. For instance, in 2024 trials on the post-Panamax bulker Chinook Oldendorff, three Norsepower rotor sails achieved approximately 9% fuel savings on North Pacific routes where slow steaming was employed, contributing to broader decarbonization efforts in the dry bulk sector. The compatibility of slow steaming with alternative fuels further optimizes environmental performance, particularly in engines designed for low-load operations. LNG-fueled engines, when paired with slow steaming, can achieve up to 55.1% reductions in (GWP20) emissions compared to conventional at higher speeds, as lower engine loads minimize and improve combustion efficiency. Similarly, ammonia engines maintain stable performance at reduced speeds, enabling further cuts in CO2-equivalent emissions by leveraging the fuel's zero-carbon properties during extended low-power voyages. This integration is crucial for vessels transitioning to green fuels, as slow steaming helps mitigate efficiency losses associated with part-load running in dual-fuel systems. Advancements in hull and route technologies also synergize with slow steaming to boost total vessel efficiency. Air lubrication systems, which release microbubbles along the hull to reduce frictional resistance, yield 3-13% fuel savings that are particularly pronounced at lower speeds, where hydrodynamic drag is less dominant. When combined with autonomous routing algorithms that optimize paths for weather and currents, these measures can deliver up to 40% improvements in overall energy efficiency, according to 2023 analyses of multi-technology implementations. Such integrations allow operators to maintain slow steaming protocols while minimizing voyage delays, as seen in recent simulations for container and bulk routes.

Regulatory Framework and Future Outlook

Current Regulations

The (IMO) has established key frameworks to promote in shipping, indirectly incentivizing slow steaming as a compliance strategy. The Energy Efficiency Design Index (EEDI), effective since January 1, 2013, applies to newbuild ships and sets mandatory efficiency standards based on CO₂ emissions per transport work, encouraging design optimizations that align with operational practices like reduced speeds to achieve required reductions. Complementing this, the Carbon Intensity Indicator (CII), implemented from January 1, 2023, for ships over 5,000 gross tonnes, mandates annual operational carbon intensity ratings on a scale from A (best) to E (worst), with ships rated D or E required to submit corrective action plans. Compliance is frequently achieved through speed reductions of 1-2 knots, as these operational adjustments significantly lower fuel consumption and CO₂ output per unit of work without major retrofits. In the , regulatory measures directly price emissions and target , favoring slow steaming to minimize costs and meet thresholds. The EU Emissions Trading System (ETS) was extended to from January 1, 2024, covering 100% of emissions from intra-EU voyages and 50% from voyages to/from non-EU ports for ships of 5,000 gross tonnes and above; this cap-and-trade mechanism imposes costs on CO₂, CH₄, and N₂O emissions, prompting operators to adopt slower speeds that reduce overall exposure to allowance purchases. Building on this, the FuelEU Maritime regulation, applicable from January 1, 2025, requires a 2% reduction in the (GHG) intensity of energy used on board compared to levels, escalating to 80% by 2050, and promotes measures such as slow steaming alongside and low-carbon fuels to avoid penalties. Non-compliance under EU ETS incurs penalties of €100 per tonne of excess CO₂ equivalent, while FuelEU imposes fines of €2,400 per tonne of VLSFO equivalent for non-compliant energy in 2025, rising annually. At the national level, the implements vessel speed restrictions under the Endangered Species Act and , with environmental assessments prepared pursuant to the (NEPA). For example, rules propose 10-knot speed limits in seasonal zones along the East Coast to reduce vessel strikes on North Atlantic right whales, which incidentally lower emissions and through slow steaming-like operations in sensitive areas. These are reinforced by incentives in green shipping corridors, such as the U.S. Department of Transportation's initiatives promoting low-emission routes with grants and streamlined approvals for operators adopting efficiency practices like reduced speeds. In April 2025, the approved the Net-Zero Framework, combining mandatory emissions limits and GHG pricing mechanisms to support the 2023 GHG Strategy goals, further incentivizing operational measures such as slow steaming across the global fleet. As of 2025, compliance reports indicate widespread adoption of speed adjustments across the global fleet to meet CII requirements, with bulk carriers showing an average slowdown contributing to a 2.5% emissions drop since 2021, and containerships requiring annual reductions of 0.2-0.4 knots for sustained ratings. Slow steaming is poised to play a pivotal role in achieving the net-zero (GHG) emissions target for international shipping by or around 2050, with interim goals of at least 20% (striving for 30%) reduction by 2030 and at least 70% (striving for 80%) by 2040 relative to 2008 levels. To meet these ambitious benchmarks, particularly the 2040 target, industry analyses project average vessel speed reductions of 20-30% through sustained slow steaming practices, as fuel consumption and emissions scale cubically with speed, enabling substantial decarbonization without relying solely on alternative fuels. This operational strategy remains essential, as it can contribute up to 20% of required efficiency gains in the near term, complementing technological advancements to align with global net-zero pathways. Emerging trends indicate a shift toward regulated slow steaming within designated green shipping corridors, where public-private partnerships enforce speed limits and efficiency standards to accelerate decarbonization. For instance, the Singapore-Rotterdam Green and Digital Shipping Corridor incorporates slow steaming alongside zero-emission fuels to achieve 20-30% GHG reductions for large vessels by 2030, with 2025 pilots testing related sustainable practices. These initiatives also highlight social impacts, such as shifts in employment, where longer transit times may increase demand for inventory management roles while potentially reducing turnaround jobs, necessitating workforce reskilling programs to mitigate disruptions in global logistics networks. Looking ahead, challenges include integrating slow steaming with autonomous vessels and e-fuels, as could optimize dynamic speed adjustments but requires compatible , while e-fuels' higher costs may incentivize faster operations to minimize volumes needed, potentially undermining emission benefits. If unmanaged, widespread adoption could extend round-trip times by 10-20%, risking bottlenecks and up to 15% disruptions in global trade volumes through modal shifts to higher-emission alternatives like air freight. Despite these hurdles, optimistic forecasts project significant drops in emissions in the near term through integration of slow steaming with digital routing and renewable energy sources, positioning it as a bridge to full and adoption by mid-century.

References

  1. [1]
    Slow steaming in container shipping | Port Economics, Management ...
    Since 2007, shipping lines started to implement slow steaming by reducing their vessels' commercial speed from 22-23 knots to 18 knots or even slower.<|control11|><|separator|>
  2. [2]
    How 'slow steaming' reduces emissions from shipping
    Slow steaming involves ships cutting their speed to conserve fuel. It began in the early 2000s as a response to rising bunker fuel prices.
  3. [3]
    [PDF] The impact of slow ocean steaming on delivery reliability and fuel ...
    Notteboom and Cariou (2011) provided data from mid 2008 to late 2010 to show that (i) slow steaming has become an industry-wide trend; (ii) slow steaming leads ...
  4. [4]
    Regulated Slow Steaming in Maritime Transport - CE Delft - EN
    Regulated slow steaming has a number of advantages: it is the most cost effective way to reduce ship emissions, and if implemented correctly, it is cost free ...
  5. [5]
    Slow steaming: The good, the bad and the pointless | Case Studies
    Sep 16, 2024 · Slow steaming is a ship operation strategy aimed at reducing fuel consumption and emissions by intentionally reducing engine power from its ...
  6. [6]
  7. [7]
    Slow steaming and virtual arrival | Gard's Insights
    Slow steaming means cutting speed in order to reduce fuel consumption, which for a container ship for example is mainly a function of the size of the ship and ...
  8. [8]
    Slow Steaming: How it Impacts Shippers & Carriers [+Types]
    Dec 16, 2019 · At its core, slow steaming is when there is a deliberate reduction in the cruising speed of a sea vessel. This intentional slowing down of a ...
  9. [9]
    The economics of slow steaming - Seatrade Maritime
    Oct 6, 2014 · Slow steaming is no longer a new concept to shipping. The practice of deliberately slowing down the speed of a ship is in fact a common ...
  10. [10]
    [PDF] Regulated Slow Steaming in Maritime Transport
    While in the past safety concerns have been raised in relation to very low engine loads, recent experience with super slow steaming, e.g. with Maersk, has ...<|separator|>
  11. [11]
    [PDF] The Guide to Slow Steaming On Ships | Marine Insight
    Slow steaming has successfully helped ship owners in reducing the amount of fuel needed to run ships, which in turn has lead to significant decrease in carbon ...
  12. [12]
    Slow steaming impacts on ocean carriers and shippers
    Apr 25, 2013 · Reducing vessel speed to 21 knots represents 'slow' steaming with 18 knots defined as 'extra slow' and 15 knots as 'super slow' (Bonney and ...
  13. [13]
    [PDF] Basic principles of ship propulsion
    speed power curves” in Chapter 2, the power required to propel the ship is proportional to the speed of the ship by the power of about 3 to 4, P ∝ V3 to 4.
  14. [14]
    Ship speed vs power or fuel consumption: Are laws of physics still ...
    The cube law derives from hydrodynamic principles and states that a reasonable approximation for a ship's required power (and also daily fuel consumption) is ...
  15. [15]
    Optimal ship speed and the cubic law revisited: Empirical evidence ...
    Vessels are designed to sail at speeds equivalent to 70–80% engine load, which is where the SFC function reaches its minimum (MAN Diesel & Turbo, 2004).Missing: percentage | Show results with:percentage
  16. [16]
    Specific Fuel Consumption [g/kWh] for Marine Engines
    Mar 31, 2025 · Specific fuel consumption for marine engines ranges from 155 to 225 g/kWh at optimal load, but can reach 1500 g/kWh at 1% load.
  17. [17]
    [PDF] MariFuture Development Paper;
    May 1, 2017 · SFC is a minimum (i.e. efficiency is a maximum) for a certain load level; typically for engines it is in the range of 70 to 90% of an engine's ...
  18. [18]
    Will Plummeting Bunker Fuel Prices Lead to End of Slow Steaming ...
    Mar 7, 2016 · In 2008, bunker fuel costs spiked to about $700 per metric ton, up sharply from the $150 or so range seen in 2000-2004.Missing: peak | Show results with:peak
  19. [19]
    (PDF) Slow Steaming in Container Shipping - ResearchGate
    This paper gives a short overview of the slow steaming history as well as the widely assumed coherence between a ship's speed and its fuel consumption.
  20. [20]
    Slow steaming and a new dawn for wind propulsion: A multi-level ...
    Slow steaming demonstrates how a socio-technical transition may emerge in response to landscape pressures which placed stress upon the shipping regime. In ...
  21. [21]
    Maersk: 'slow steaming is here to stay? - FreightWaves
    Aug 25, 2010 · Maersk said in 2007 it began slow steaming, a practice that “involves a vessel operating at lower-than-average speeds at different legs along a ...Missing: Emma | Show results with:Emma
  22. [22]
    World Shipping Council: Cleaner fuel will cost twice as much
    May 4, 2008 · “Bunker prices have risen 87 percent since the beginning of 2007. Fuel costs represent as much as 50-60 percent of total ship operating costs ...
  23. [23]
    Effects of container ship speed on CO2 emission, cargo lead time ...
    In 2008, high oil price forced carriers to cut sailing speed down, for instance, from 24 to 20 knots in the Asia-Europe trades, 20 to 16 knots in Atlantic ...
  24. [24]
    [PDF] AP Møller - Mærsk A/S Interim Management Statement
    Oct 13, 2015 · Fuel prices rose throughout the third quarter of 2009. To offset the rising fuel costs, Maersk Line has introduced “super slow steaming”, which.
  25. [25]
    A Study on the Impact of Slow Steaming on Containership ...
    Apr 30, 2024 · First, it was found that containerships will undergo degradation in the CII rating every 3 or 4 years without slow steaming. Second, a speed ...
  26. [26]
    Strategies to Reduce Fuel Consumption in Shipping - VoyageX AI
    Strategies include optimizing vessel speed, dynamic route planning, predictive maintenance, fuel forecasting, and emissions tracking.
  27. [27]
    [PDF] Just In Time (JIT) Arrival Guide - GreenVoyage2050
    The purpose of this JIT Arrival Guide is to provide information and proposals to the port and shipping sectors as well as port and maritime administrations on ...
  28. [28]
    The impact of slow ocean steaming on delivery reliability and fuel ...
    According to the World Shipping Council WSC (2008), fuel costs represent as much as 50–60% of total operating costs. In the past when the fuel price was much ...
  29. [29]
    Effects of Slow Steaming Strategies on a Ship Fleet - ResearchGate
    Currently, container ships operators have implemented slow steaming (SS) strategies in their fleets to improve the profit margins by reducing operational costs.Missing: planning | Show results with:planning
  30. [30]
    An overview of seafarers' engagement and training on energy ...
    This study delves into the pivotal role of seafarers in achieving energy-efficient ship operations, which is crucial for mitigating climate change.
  31. [31]
    Engine de-rating - GreenVoyage2050
    De-rating the engine offers the possibility to lower the vessels maximum speed, specified maximum continuous rating (MCR), and thereby optimize actual load ...
  32. [32]
    Wärtsilä Fixed Pitch Propellers - FPP
    The main reasons for a propeller replacement are: Improved efficiency; Change in operating profile, such as slow steaming; The propeller is too severely damaged ...Missing: ducted | Show results with:ducted
  33. [33]
    [PDF] Slow steaming – a viable long-term option? - Wärtsilä
    Slow steaming reduces fuel costs by lowering ship speed, but increases voyage time. It offers flexibility and reduces emissions, but long-term viability needs ...
  34. [34]
    Slow Steaming of Ships: Optimization of Ship's Main Engine
    Aug 22, 2019 · Slow steaming up to 50 to 55 % load can be done generally on most engines without harm in long terms if certain precautions are taken.
  35. [35]
    The Impact of Slow Steaming on Fuel Consumption and CO2 ... - MDPI
    Mar 22, 2023 · The main goal of applying slow steaming in shipping is to increase energy efficiency, but also for older ships to meet EEXI requirements [8]. ...
  36. [36]
    Slow Steaming (SS) or Super Slow Steaming (SSS) for Container ...
    Jan 11, 2011 · What is slow steaming or super slow steaming? It is used to reduce the speed at which ships travel. · Why slow steaming? · What are the benefits ...
  37. [37]
    Ocean shipping lines cut speed to save fuel costs - Los Angeles Times
    Jul 31, 2010 · The sharp improvement came with the help of a 9% saving in fuel consumption because Maersk's ships slowed down. ... “We continue our slow steaming ...Missing: $2.4-2.8 | Show results with:$2.4-2.8
  38. [38]
    What Are the Benefits of Slow Steaming? → Question
    Apr 30, 2025 · Slow steaming significantly cuts fuel use and emissions by reducing vessel speed, lowering operational costs and aiding compliance with ...
  39. [39]
    Analysis of Slow Steaming of Ship and Its Impacts - ResearchGate
    Aug 6, 2025 · Slow steaming involves purposefully lowering ship speed to reduce bunker fuel consumption and also results in lower emissions. Therefore ...Missing: origins | Show results with:origins
  40. [40]
    Optimal Slow Steaming Speed for Container Ships under the EU ...
    Slow steaming is an operational measure in ocean-going vessels sailing at slow speeds. It can help climate mitigation efforts by cutting down marine fuel ...
  41. [41]
    How the shipping sector could save on energy costs – Analysis - IEA
    Mar 28, 2025 · In 2023, this saved 1.8 mb/d of oil and USD 60 billion USD in fuel costs. Still, there remains ample scope for further improvements – in ...
  42. [42]
    [PDF] a short-term measure to reduce maritime GHG emissions - CE Delft
    Oct 18, 2017 · This can offset a share of the energy- efficiency gains brought about by slow steaming. Yu, et al. (2012) provide an example of a slow-speed ...
  43. [43]
    From slow steaming to speed optimization - FreightWaves
    Feb 27, 2013 · To find the optimal speed for a ship, the charterer must take into account both its charter cost, which increases as a ship slows down and days ...
  44. [44]
    Assessing the macroeconomic and social impacts of slow steaming ...
    Feb 27, 2023 · According to this analysis, slow steaming has been used to tackle the negative economic impacts of the Sulphur Directive in the short sea ...Transport Dependency · Transport Cost · Cost-Effectiveness
  45. [45]
    'Super' slow steaming makes a comeback as surplus capacity builds
    May 26, 2023 · Average spot rates from Asia to the U.S. East Coast are currently at $2,401 per FEU, 15% above the levels of May 2019, while rates on Asia-U.S. ...
  46. [46]
    [PDF] Regulated Slow Steaming in Maritime Transport - CE Delft
    Regulated slow steaming involves speed limits to reduce greenhouse gas emissions from ships, proposed by the Clean Shipping Coalition. Reducing speed reduces ...Missing: trials | Show results with:trials
  47. [47]
    Slow Steaming as a Sustainable Measure for Low-Carbon Maritime ...
    The results indicated that when constant transport work was maintained, yearly CO2 emissions decreased by −16.89% with a 10% speed reduction, −21.97% with a 20% ...
  48. [48]
    Is slow steaming a sustainable means of reducing CO2 emissions ...
    This paper shows that slow steaming has reduced emissions by around 11% over the past 2 years; close to the target of a 15% reduction by 2018.
  49. [49]
    [PDF] NOx controls for shipping in EU Seas - Transport & Environment
    The use of slow steaming will reduce the emissions of NOX approximately in proportion to the reduction in fuel consumption. For an individual ship there may ...
  50. [50]
    Environmental economic analysis of speed reduction measure ... - NIH
    Apr 4, 2023 · By using the speed reduction approach, the quantity of fuel is saved by a noticeable percentage as shown in Fig. 4. When the service speed ...
  51. [51]
    What is Ship Energy Efficiency Management Plan? - Marine Insight
    Jan 11, 2024 · Slow steaming has been a proven strategy to reduce the fuel consumption of the ship saving hundreds of dollars in fuel cost to the owner.
  52. [52]
    Slowing deep-sea commercial vessels reduces underwater radiated ...
    Jul 23, 2019 · A two-month voluntary vessel slowdown trial to determine whether slowing to 11 knots was an effective method for reducing underwater radiated vessel noise.Ii. Methods · E. Noise Reduction Analysis · Iii. ResultsMissing: steaming | Show results with:steaming
  53. [53]
    Slow steaming: Decreasing speed cuts emissions, wildlife collisions ...
    Jan 20, 2025 · Research shows that a 10 per cent speed reduction can decrease noise pollution by 40 per cent, while a 20 per cent speed reduction can decrease ...Missing: 2024 | Show results with:2024
  54. [54]
    Reducing the Risk of Ship Strikes to Endangered Whales
    Fatal ship-strike risk is reduced by nearly 50% when vessels slow down from 15 knots to whale-safer 10 knots. 0%. Global shipping traffic overlaps with about 92 ...Missing: steaming collision 50-70%
  55. [55]
    When Ships Slow Down, Everybody Wins, Including Endangered ...
    The slower vessel speeds last year reduced the risk of fatal whale strikes by 50 percent in the reduction zones, according to the Blue Whales and Blue Skies ...
  56. [56]
    Ship emissions reduction via slow steaming without disrupting the ...
    This paper focused on addressing the challenges of applying “slow steaming” as a measure of cutting emissions.
  57. [57]
    Two research projects launch to investigate changing marine ...
    Oct 27, 2025 · Both projects, supported by the Knowledge Hub, aim to address critical gaps in our understanding of how marine light environments are changing, ...Missing: slow steaming reduced
  58. [58]
    Smart Steaming: A New Flexible Paradigm for Synchromodal Logistics
    Smart steaming is about defining a medium speed execution of shipping movements and the real-time adjustment (acceleration and deceleration) of traveling ...
  59. [59]
    SYNCHRO-NET - Smart Steaming and De-stressing the Supply Chain
    Smart steaming is an enhanced version of the well-known slow steaming approach that has been used by shipping companies for many years as a way to reduce fuel ...Missing: technologies | Show results with:technologies
  60. [60]
    Synchro-modal Supply Chain Eco-Net - CORDIS - European Union
    Aug 16, 2022 · SYNCHRO-NET will demonstrate how a powerful and innovative SYNCHRO-modal supply chain eco-NET can catalyse the uptake of the slow steaming ...
  61. [61]
    Global Maritime Energy Efficiency Partnerships Project (GloMEEP)
    GloMEEP is a GEF-UNDP-IMO project aimed at supporting the uptake and implementation of energy efficiency measures for shipping, thereby reducing greenhouse ...Missing: steaming | Show results with:steaming
  62. [62]
    Smart Steaming and Hinterland Logistics Optimization
    ### Summary of Smart Steaming Implementation, Real-Time Data, and Savings Examples
  63. [63]
    Maersk Launches AI-Powered Vessel Routing Platform to Cut ...
    Global shipping leader Maersk has officially launched an AI-powered routing platform designed to reduce fuel consumption and carbon emissions across its global ...
  64. [64]
    US transport and shipping companies face hurdles in AI adoption
    Aug 21, 2025 · Current AI usage: The most common AI use cases are fleet management and telematics optimization (31%) and AI-driven route optimization (29%).
  65. [65]
    Impact of Wind-Assisted Propulsion on Fuel Savings and Propeller ...
    The velocity prediction program (VPP) presented in the paper suggests a propeller power reduction of approximately 10% when slow steaming in winds of 13 knots.Missing: amplification pilots
  66. [66]
    Oldendorff post panamax bulker gets trio of Rotor Sails
    Nov 5, 2024 · Chinook Oldendorff expected to reap 9% fuel consumption savings from wind propulsion on its North Pacific route.
  67. [67]
  68. [68]
    Emission performance of ammonia-fueled, four-stroke marine engines
    Jun 3, 2025 · LNG-fueled four-stroke engines are known to suffer from methane slip (especially at reduced engine loads) causing significant greenhouse gas ( ...Missing: slow steaming compatibility
  69. [69]
    [PDF] Route-based assessment of innovative technologies to reduce ship ...
    May 13, 2019 · Air lubrication systems can reduce route-level fuel consump- tion and emissions by approximately. 3%–13%, depending on draught and ship speed.
  70. [70]
    Making ships more energy efficient helps achieve short-term goals
    Apr 21, 2023 · The study found a 34-40% increase in a ship's energy efficiency could be achieved in multiple ways that are not directly linked to the type of fuel a ship uses.Missing: autonomous routing
  71. [71]
    [PDF] The Energy Efficiency Design Index (EEDI) for New Ships
    The regulation only requires that ships have a plan, but approval of the plan's contents and tracking of the ship's progress of SEEMP details by the flag.
  72. [72]
    Assessment of ship speed, operational carbon intensity indicator ...
    This study establishes a speed model including CII penalty for time charter ships. Results show that speed reductions of a time charter ship of 10 %, 20 % and ...
  73. [73]
    Reducing emissions from the shipping sector - EU Climate Action
    Since January 2024, the EU's Emissions Trading System (EU ETS) has been extended to cover CO2 emissions from all large ships (of 5 000 gross tonnage and above) ...Eu Action · Inclusion Of Maritime... · Legislative ProcessMissing: steaming | Show results with:steaming
  74. [74]
    FuelEU Maritime: Regulation insights & support - DNV
    This will start at a 2% reduction in 2025, increasing to 6% in 2030, and accelerating from 2035 to reach an 80% reduction by 2050. FuelEU Maritime - GHG ...Compliance tab · FuelEU Maritime white paper · FAQ · Services
  75. [75]
    EU ETS Compliance - Emissions Trading System - DNV
    Companies that fail to surrender allowances are liable to an excess emissions penalty of 100 Euros per tonne of CO2 and are still liable for surrender of the ...
  76. [76]
    FuelEU Maritime's Targets, Compliance, and Penalties - ZeroNorth
    Sep 25, 2024 · The regulation sets gradual targets for reducing the GHG intensity of energy used on-board ships, starting from 2025 and becoming more stringent towards 2050.
  77. [77]
    [PDF] Draft Environmental Assessment for Amendments to the North ...
    Jul 20, 2022 · The proposed regulations restricting the transit speed of certain vessel sizes to 10 knots or less within certain areas and seasons are expected ...
  78. [78]
    Global bulker fleet 'slows down' in response to decarbonization ...
    Oct 11, 2024 · The bulk carrier sector is seeing a downturn in average speeds, resulting in a decrease of 2.5% in carbon emissions since 2021.
  79. [79]
    [PDF] A Study on the Impact of Slow Steaming on Containership ...
    (2023) report that the benefits from speed reduction of post-Panamax containerships differ depending on the sailing routes, the location and the month.
  80. [80]
    IMO's work to cut GHG emissions from ships
    This Strategy sets clear targets and actions to decarbonize international shipping: Net-zero GHG emissions from international shipping by or around, i.e. close ...Missing: slow | Show results with:slow
  81. [81]
    Shipping industry still at sea as it tries to navigate to net zero | Reuters
    Jun 26, 2025 · Shipowners must cut emissions by 65% by 2040 under expected IMO rules ... There's nothing that prevents you from slow-steaming, or equalising your ...Missing: projections | Show results with:projections
  82. [82]
    Expert Assessments of Maritime Shipping Decarbonization ...
    Apr 9, 2025 · They attribute most of the past carbon intensity reductions to slow steaming, considered a low-hanging fruit in shipping decarbonization ...
  83. [83]
    Rotterdam and Singapore Strengthen Collaboration on Green and ...
    Mar 25, 2025 · The two ports have since brought together 28 partners across the entire container shipping value chain to drive the deployment of sustainable fuels.Missing: EU | Show results with:EU
  84. [84]
    [PDF] Benefits and Challenges of Autonomous Vessel Use on the ...
    social challenges. Traditional technical or operational solutions, such as building larger ships or slow steaming, have reached their limitations to.
  85. [85]
    [PDF] A pathway to decarbonise the shipping sector by 2050 - IRENA
    2 “Slow steaming” refers to the fuel-saving practice of operating a vessel at an average speed that is well below its design speed. Page 30. A PATHWAY TO ...