Slow down

Is forcing ships to slow down an easy way of cutting shipping emissions? Just a year ago the 173 countries represented at the International Maritime Organization (IMO) agreed that shipping would reduce its carbon emissions by at least a half by 2050.

Now several proposals have been tabled at the IMO that could see speed limits put on the global shipping fleet. Despite big strides in efficient engine technologies and fuel-saving operational practices, an ever-expanding fleet, servicing growing global trade volumes, means that without radical action, emissions from shipping will rise. International shipping already accounts for around 2.2% of global CO2 emissions. These emissions are projected to grow between 50 and 250 percent by 2050 if no action is taken.

To achieve its goal of halving emissions by 2050, the IMO has set-out a strategy involving a reduction of CO2 emissions of 40% by 2030. It hopes to reach this goal by developing short-term measures such as removing market barriers, improving operational energy efficiency and developing technologies for zero-carbon fuels that will deliver additional CO2 reductions before 2023; mid-term measures to be adopted between 2023 and 2030 aimed at fostering innovation and starting the deployment of alternative fuels plus longer term measures that will eventually achieve full decarbonisation of international shipping within this century.

This May the IMO’s Marine & Environment Protection Committee (MEPC) meets to examine detailed short-term proposals to reduce CO2 emissions and put shipping on the path to meeting IMO’s 2030 40% reduction ambition.  But without the realistic prospect of low-carbon fuels taking the place of oil as the main power source for ships’ engines by 2030, several proposals have been submitted to the MEPC involving bringing ships’ speeds down.

The first of these is a proposal by the Clean Shipping Coalition, an environmental lobby group, which recommends ships be required to calculate their annual average speed by working out the total distance sailed and the hours spent underway. Japan has submitted a proposal which is a goal-based improvement measure involving a design efficiency goals to limit engine power. France, on the other hand, is advocating the introduction of a speed limit as soon as possible and bringing in a maximum annual fuel consumption per ship after 2020. Under this plan a ship would not be allowed to use more fuel or emit more CO2 than it had done in 2019. France also wants the IMO to come up with “a mode of enforcement of the measure using existing technological and legal means”, which will include sanctions for non-compliance.

Of course, the feasibility of any scheme depends on whether not the speed of a ship can be accurately monitored by not just the ship, but also the regulator. Thanks to AIS, this data is publicly accessible and MarineTraffic is an IMO partner, providing its data to numerous studies and projects.

According to IMO’s GloMEEP, a GEF-UNDP-IMO project aimed at supporting energy efficiency measures for shipping, by simply reducing a ship’s speed by 10%, its fuel consumption can be lowered by almost 20%.

But if cutting a ship’s speed saves a ship-operator fuel costs and significantly reduces shipping’s carbon footprint, why doesn’t everyone just slow down? Why aren’t engine manufacturers forced to build less powerful turbines?

Unfortunately, it’s not as simple as that.

In the first instance, ships move at the behest of charterers. Our world of just-in-time logistics means that supply chains rely on wafer thin time margins. More time in transit means more inventory held and therefore more cost to the charterer and ultimately the consumer. This is particularly relevant to the container line trade. MarineTraffic data shows that between January 2018 and April 2019, the average speed of a 14,500 + TEU containership was 16 knots, significantly higher than a dry bulk capesize vessel moving coal or iron ore which averaged 11 knots over the same period.

Secondly, the weather. Ships need to fight the waves in poor weather and therefore consume more power. There are very good safety reasons as to why a ship would want access to more engine power when needed.

Thirdly, slow steaming can inflict increased wear and tear on ships’ engines. Ship engines are designed to run constantly at full load, not at a reduced capacity.

In fact ships slowed down significantly in 2008 when the freight markets collapsed. Market forces mean that ships naturally slow down when rates are bad and speed up when rates are good and they chase cargoes and berth slots. With rates for the largest dry bulk carriers having this year hit rock bottom (average daily capesize timecharter rates as reported by the Baltic Exchange were as low as $3460 per day in early April), dry bulk ships have slowed down.

Source: Baltic Exchange and MarineTraffic

Mandatory speed limits potentially take away the flexibility prized by shipping companies to manage their available capacity – speed as a variable helps them to manage this.

Indeed, the trade association representing dry bulk shipowners (INTERCARGO) has argued that introducing speed limits will simply result in more ships being built and therefore increased CO2 emissions.

But it is not just a ship’s average speed which impacts its fuel consumption, but its variable speed. Ships travelling at a constant speed consume significantly less fuel than a ship speeding up and slowing down. That’s why initiatives focusing on stopping ships racing to reach an available berth only to then spend time idling outside port are so important. MarineTraffic is a founding member of the IMO’s Global Industry Alliance, which is focusing on Just-In-Time operations to cut the time ships spend idling outside ports can help cut emissions. 


Average vessel speed 2018-today, based on MarineTraffic AIS data

For the purposes of this exercise, vessel speeds below 3 knots have been excluded.    

Vessel Type Average speed (knots)
Jan 2018 – April 2019
Containerships 14.6
Dry Bulk 11.3
Tanker 11.4
LNG 14.1
LPG 13.4
Breakbulk 12.1


Vessel type Average speed (knots)
Jan 2018 – April 2019
Container, Small Feeder (0-999 TEU) 12.5
Container, Feeder (1000 – 1999 TEU) 13.9
Container, Feedermax (2000 – 2999 TEU) 14.1
Container, Panamax (3000 – 5099 TEU) 14.6
Container, Post Panamax (5100 – 9999 TEU) 15.8
Container, New Panamax (10,000 – 14,999 TEU) 15.9
Container, ULCV (>14,500 TEU) 16
Breakbulk, Handymax (40,000 – 59,999 DWT) 11.8
Dry Bulk, Handysize (<39,999 DWT) 11.2
Dry Bulk, Handymax (40,000 – 59,999 DWT) 11.3
Dry Bulk, Panamax (60,000 – 79,999 DWT) 11.4
Dry Bulk, Post Panamax (80,000 – 199,999 DWT) 11.3
Dry Bulk, Capesize (120,000 – 199,999 DWT) 11
Dry Bulk, VLBC/ULBC (>200,000 DWT) 11.6
LNG Carriers (ALL) 14.1
LPG Carriers (ALL) 13.4
Wet Bulk, Handysize (<39,999 DWT) 10.5
Wet Bulk, Handymax/MR (40,000 – 59,999 DWT) 11.8
Wet Bulk, Panamax/LR1 (60,000 – 79,999 DWT) 11.6
Wet Bulk, Aframax/LR2 (80,000 – 119,999 DWT) 11.1
Wet Bulk, Suezmax (120,000 – 199,999 DWT) 11.4
Wet Bulk, VLCC/ULCC (>200,000 DWT) 12

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Bill Lines
Bill is a director of London based maritime public relations firm Navigate PR and has been working with MarineTraffic since 2013.