Depens on how you pose the question. Ships can move far more goods per horsepower than a truck, so they should pollute less. OTOH ships usually burn much cruder (dirtier) oil, so smoke puff by smoke puff they pollute more.
Everyone pollutes the air to a certain degree. Everytime someone uses a cooking fire, electric stove, automobile, throws away trash or garbage, or even excretes bodily waste, or passes gas they (we) are producing pollution of one or more types. It isn't that we all pollute but to the degree that we all pollute. Some pollute more than others, for various reasons.
factories
It pollutes the air
non-point source pollutions
Electric power plants
the car that pollutes more is the three wheeler and the BMW X5
Buses, trucks, planes, ships, some boulders, whales, large trees
Diesel
=The US vehicles included trucks planes ships trains and many more.=
They are exported by ships, trains and trucks.
trucks, planes, and ships
A car
Cars, trucks, ships, trains and bicycles.
they taveled by trains, houses , trucks and ships
In WW2, some ships also transported tanks, trucks, planes and other vehicles, not mentioning food and medical supplies.
fleet : a group of ships fleet can also refer to a group of trucks, ie. The moving company owns a large fleet of trucks
Vegetable oil