Cargo Ship Speed Comparison: How Fast Do They Go?
It is well-known that most of the world’s goods and fuel are transported by sea. Often travelling thousands of miles across the world, ships need to be able to achieve high enough speeds to get to their destination in a reasonable amount of time. But just how fast do they go?
Some cargo ships are able to travel at phenomenal speeds. The Maersk Boston is a 294 metre container ship capable of steaming at an incredible 37 knots (42.5mph). This means that, in theory, she could transport tens of thousands of tonnes of cargo from Dublin, Ireland to Lisbon, Portugal in just over 24 hours.
However, although there are many cargo ships that can achieve these very high speeds, this does not mean that they actually sail at these speeds.
Not only is it very bad for fuel economy to sail at these speeds, but it would also be unsafe to travel at such speeds in congested waters.
What is the average speed of a cargo ship?
Different types of ships tend to travel at different average speeds. The table below shows an example of some typical average voyage speeds:
|Ship type||Average service speed|
|Vehicle carrier||15 knots|
|Container ship||14 knots|
|Bulk carrier||11 knots|
|Oil/Chemical/Gas tanker||10 knots|
|General cargo ship||9 knots|
Congested traffic areas, navigational hazards, local laws, and fuel economy, all affect the speed at which a ship can travel.
It’s also unlikely that a charterer would set an ETA for a ship which would require her to travel at maximum speed, as this leaves no room for delays or error.
What speeds are cruise liners and superyachts capable of?
Queen Mary 2 is capable of 30 knots as she runs a liner service between Southampton and New York. She is able to achieve this speed for most of the journey across the Atlantic, because the route is essentially a straight line and there is little to no shipping traffic.
30 knots is a much higher speed than other cruise ships, most of which have a maximum speed of just over 20 knots.
Superyachts are built as top-end luxury vessels, and as a result they are often built with the capability of achieving incredible speeds. The superyacht Foners is considered to be the fastest yacht ever built, and can hit 70 knots. There are many superyachts which can achieve in excess of 60 knots.
As we can see, when fuel costs and making a profit are not considerations, ships can be built to achieve very impressive speeds!
Cruise ship itineraries – why are they different to cargo ships?
When considering cruise ships, we need to look at sailing speeds a little differently to cargo ships.
On certain cruise ship itineraries, for example in the Caribbean, it may not be very far between ports. This means that the required sailing speed to get from one port to the next can be very low.
This allows cruise ships the opportunity to ‘slow steam’ between ports. There are many benefits to slow steaming, but slow steaming isn’t just for cruise ships.
Over the last fifteen years, slow steaming has become more and more popular for cargo ships due to the financial and environmental advantages it offers.
What is slow steaming?
Slow steaming is the term for when a ship purposely sails slower than its maximum speed. There is an exponential relationship between a ship’s speed and the fuel consumed, so it is understandable that shipping companies want to try to reduce the speeds of their ships.
Although there can be some downsides to slow steaming, for example a negative impact on some machinery which is designed to run at higher loads, there are many benefits:
|Benefits of slow steaming|
|Lower fuel consumption and costs|
|Improved reliability of certain machinery|
|Less pressure on the crew to meet tight ETAs|
|Reduced anchorage costs and waiting times on arrival in port|
|Reduced impact on marine mammals|
Ships’ engines are typically designed to run at between 70-85% load during continuous operation. Slow steaming means reducing the load to around 50-55%.
Because of this, slow steaming strongly relies on the ship’s Chief Engineer and his team to ensure that the ship’s machinery is optimised and ready for slow steaming to reduce damage to the engines and other machinery.
Our video below explains more about slow steaming and why it’s become so popular with shipping companies in the last fifteen years:
Are there speed limits at sea?
There is no universal speed limit at sea. This doesn’t mean that ships can go as fast as they like, however.
The Collision Regulations state that ships must at all times proceed at a ‘safe speed’, although no numerical limit is prescribed – it is up to the ship’s Captain and officers to judge what is an appropriate safe speed based on a number of factors including:
|Most important factors affecting the determination of ‘safe speed’|
|The proximity of other ships in the area|
|Visibility – is it foggy, or are shoreside lights making it difficult to see other ships’ navigation lights?|
|How much depth and width of water is available|
|How manoeuvrable the ship is|
It is generally considered that when other ships are in the area, a slow speed is a safe speed. This is because it gives the navigators more time to think and act, it allows the ship to be stopped more effectively, and if a collision does occur, the damage will be less.
Ports and harbours, however, will have their own numerical speed limits – usually in the range of 6-10 knots. This is not only because of the closeness of hazards when in port, but also because a speed of above 6 knots is not considered safe when using or interacting with tugs in harbour.