Ship Assist - Push/Pull vs on the line

Dear all,

Following Gcaptain since a while and now new on the forum. I wanted to say first thank you for the great job made by John Konrad.

My question concern tugs.

I have been tug master the past 10 years working with the 2 differents methods push/pull (on the side) and on the line.

I know in America you most of the time use the push/pull method which work well for tankers and bulks but how do you proceed with container ship with their long flares?

Do you use ATD or mainly ASD tug?

Thank you


Have to be connected somehow if you are referring to assisting. I believe there is a designed reason why the modern tractor tugs mount the wheelhouses low and close to midships to avoid the rake/flare as much as possible.

I don’t have any experience with ship assist but there are several members here that do.

I worked on car carriers and what I’ve seen is that working “push pull” the tugs put a line up and then the fwd tug will slide aft to work a clear spot not under the flare.

Usually the pilot and tug operator will discuss this before the tugs make up if it is going to be an issue.

There is a lot of variation between ports in how things are done. I have not done much ship docking in recent years, but I occasionally do some. It’s always with conventional twin screw tugs. It’s been four years since I’ve towed a barge with a single screw tug, and about 30 years since I’ve docked a ship with a single screw tug. I’ve never run a tractor tug.

Typically, the pilot will tell the tug where he wants it positioned, and what, if any, lines to put up. The pilot will tell the ship where to put the lines from the tug. Often the tug captains and pilots work together all the time taking the same, or similar, ships to the same berths. Each knows what the other is going to do, and when, long before it happens.

Sometimes nobody knows each other. Sometimes there is a prima dona pilot who makes things difficult. Sometimes there is a young tug Captain who has never docked a ship before on a tug that is not well suited for ship docking. Sometimes you have to work with the low bidder that’s available. In some ports there are very few ship calls and no tugs. The tugs may come from hundreds of miles away to dock a ship in ports such as Adak, Alaska.

A tractor tug will only have one line up. A conventional twin screw tug will have one line up, and possibly a second line to the outboard shoulder bitts. Both lines may be in the same chock on the ship, or the outboard line may be one chock forward. The use of single screw tugs for ship docking has become uncommon, except for “hold in” jobs, but a single screw tug would probably put up at least two lines and maybe three.

The most powerful tug will usually be placed at the bow. The further forward the tug is the more leverage (turning power) it will have. Pushing against the bulbous bow, if possible, works well.

Personally, I don’t like being positioned under the anchor, especially with a line up, and especially approaching a dock. Obviously, the tugs need to be positioned where the mast, wheelhouse, etc. will clear the flare of the ship. Where you can keep clear of the flare also depends on the speed of the ship, current, etc.

Ship docking is best left to tractor tugs and people who work together in the same port and do it everyday.


Agree Tugsailor. Way back when , had quite a few single screw tugs assisting. Had to run a backing line off the the stern quarter as they backed to the port and would flop alongside when I wanted them on a 90. Even with some twin screws if their was current. Always approached the dock rather slowly., That was prudent in itself. Depended on what side of the of dock the rig was going where to put the backing line. Tractor tugs changed a lot of that extra work, as long as you weren’t going at excessive speed. They are less effective trying to stay up with the vessels trying to back and stay on a 90. Tractors are the way to go of course, but you have to help them help you.


When making deliveries to ULCCs at anchor with a swell running, another area to avoid other than the bow flare is the stern counter. I expect that would apply even more to tugs with their relatively low freeboard.

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Thank you.

I am actually working on a thesis comparing the both method.
Push pull and on the line (bow to bow or Stern to bow)
I will have a look regarding the conventional way as push pull!

Hi seaeagle,

Both techniques push/pull and on the line are using connection.

Trying to compare the efficiency of each.

Thank you

From my perspective from the ship side, I prefer push pull. On the line or indirect works well for getting in and out of locks, but once we are talking about pushing alongside a berth, the direct push alongside the quarter or shoulder that pins my ship to the fenders is much appreciated. On the line can be useful for stemming the tide in a high current docking situation, but from what I have seen, particularly on the stern, the tug just pulls the ship back off the berth while you are trying to run lines.

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Handling ships “on the line”, if they call it that, is uncommon in the US.

I think of “on the line” as primarily a European ship handling method. It’s a hold over from the era of single screw tugs with the towing bitts or towing hook at least amidships.

‘On the line” may be the only way to handle a ship in a lock, dry dock, or narrow slip.

I’ve watched ships being handled “on the line” in Europe. It works well and they are very good at it. There are some interesting videos. The Nautical Institute and others have published books about ship handling with tugs.

In some places there is a lot of barge handling “on the wire.” British Columbia being the prime example.

I think that’s the case with a car ship in Bremerhaven. They routinely moor / unmoor there in gale force winds. I’ve had as many as four tugs.




From this post:

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The ship I was on had a 2000 hp bow thruster. In that case the forward tug can go further aft and the heading controlled with the trruster.

That works good for a flat landing because the heading can be controlled precisely using the thruster control on the wing. That method avoids the delay between relaying an order to the tug and the response.

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Typically with tractor tugs, they can be just as efficient if you have them through the centerlead on the stern (I assume what you mean when you say “on the line”?), or if you have them on the quarter in a push/pull.

Maneuvering differences come into play where the flare of the stern is too large and the tug who is center lead will have to pay out a bunch of line to get up past the flare. Then when you ask them to back it takes them longer to get into their line.

If you have the tug on the quarter in a push/pull, it is much faster for them to back into their line, since they don’t have nearly the same amount of line out.

Where the tugs get placed really depend on the pilot. If the pilot wants to run hot and then hit the brakes, that aft tug will typically go in the center lead chock where they can slow down the quickest. If docking at a typical tanker dock where there isn’t a lot of structure, just some dolphins and catwalks, the tug would probably stay in the center lead (assuming they can work around the flare), and be effective. However, if approaching a flat faced dock where landing flat is paramount, the tug may be shifted to the quarter to give the pilot more precise and quicker control over the movements.

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Thank you all,

Yes indeed, when talking “on the line” I mean connected center lead. I was used to work work with this method in Rotterdam.
When I was working in Carrabean, we were using the push pull method on the side (but only on tankers)

When on the line connect center lead, we worked with a very short tow, even on ULCV and were coming to push on the side only when close to the berth paying out the necessary tow length to come on the flat.

I was wondering how efficient can you be working push pull on the side with big container ship with big flare shape. Your tug will be located almost amidship resulting in a poor moment (I guess). As you can see on the picture!

If in US you are using mostly or only push pull on the side. How do you manage locks and dry docks entries?

Thank you all for your time. So interesting to exchange.

Captain’s Hagues Cauvier’s article

In the U.S. push pull is more common than in Europe but on the line is used as well.

I don’t know how many sea ports in the U.S. have locks, none that I’ve been to. For dry docks typically lines are run between the ship and dock and the tugs are let go before entry, that’s been my experience anyway, including one drydocking in Europe.

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Thank you Kennebec_Captain,

As I can see we use the same procedure for the dry dock.

I am looking for some harbor pilot or ASD/ATD TUG captain to have a quick exchange.

If some are willing to help. I will appreciate it.


The only locks for large vessels that I can think of in North America are in the Great Lakes system such as the Welland Canal (bypassing Niagara Falls), and Soo Locks (entering Lake Superior).

The Saint Lawrence Seaway Commission is currently building six small, Glosten designed, tractor tugs at Washburn & Doughty.

The relatively small ships (mostly factory trawlers) transiting the Ballard Locks in Seattle do not use tugs, unless being towed dead ship “on the line.”

There are tug and barge locks on the inland rivers and the ICW inside the Gulf of Mexico. It’s all pushing ahead.

Thank you for those info!