Where is ‘this part of the world’?
The Tug/Barge idea started as a result of the US overloaded crew compliment requirements for tankers (post ww2)
In the post war era a ‘large’ coastwise tanker (30K bbls) was required to have a 25 to 29 man crew! Industry was digging for a way to reduce manning. The CG relented in the 60’s and allowed reduced manning (down to 20 to 25 man).
That wasn’t good enough for industry profits.
So the concept of a tug and barge was developed. Tugs typically had 10 man crew, barge had 4 man crew.
That wasn’t low enough for industry profit.
Skipping the Union busting era, Atbs now run from 80K to 180K bbl barges with 7 to 9 man crew. Some companies do have slightly larger crews but I am not sure of which ones. The tugs are almost without exception under 300GT. Most are under 200GT Some are even under 100GT!. So limited tonnage licenses are all that is necessary to operate a tug pushing an ‘unlimited tonnage’ petroleum barge. Most of the barges are between 3000GT and 9999GT. I don’t know of ANY ships from anywhere in the world that runs comparable size crews.