River or coastal tug designed to push a barge tow from astern using a notch system, commonly employed on major river systems worldwide.
A pusher tug (or push-boat) is a vessel built to propel one or more barges from the stern by engaging with a notch or coupling cut into the barge transom. The tug's bow is squared-off and fitted with rubber fendering and ratchet-tensioned pushing wires or hydraulic coupling pins that lock the combination into a virtually rigid unit when underway. This arrangement is far more manoeuvrable and fuel-efficient for river operations than towing astern, particularly in confined waterways.
Pusher tug operations are the dominant mode on the Mississippi–Ohio–Missouri river system in North America, the Rhine–Main–Danube corridor in Europe, and the Yangtze and Pearl River systems in China. A single pusher tug may push 40 or more hopper barges lashed together in a tow formation (known as an integrated tow or a flotilla), with combined cargo capacity exceeding 50 000 tonnes on large rivers.
Regulation depends on the waterway: inland waterways within UNECE jurisdiction use CEVNI, while US inland waters are governed by the United States Coast Guard (46 CFR). Where pusher tugs operate in coastal or offshore tows, they may fall under SOLAS Chapter II-1 (machinery and stability) and flag State classification society rules. Unlike the articulated tug-barge, the pusher tug and its barge(s) may be coupled or separated at will without specialised equipment. See the /reference/ship-types page for tug classifications.