Harbor and Airport technical details?

[Zytukin]

Ok, this may seem like an odd question, I even think it's odd considering I've had the game for years.

But, what exactly are the technical details of the harbor and airport?

I mean, we build a harbor, trucks and ships spawn and visit it, but does it really do anything besides provide jobs, income, and look pretty?

Does freight actually get moved to the harbor from industrial zones and from the harbor to commercial zones (even if not literally tracking each piece of cargo)? If so, than what are the criteria for freight moving INSIDE the harbor zone? Like do tiles have to be withen x distance for freight to move from, for example, a rail freight station to a ship crane on the other side of a road? Since roads can divide the zone into separate pieces. Or does fright only move between adjacent tiles thus requiring all harbor tiles to be connected to each other for fright to move to a crane from a truck or rail freight station?

[JustAnyone]

TheoTown does not provide such extensive simulation.

[Zytukin]

TheoTown does not provide such extensive simulation.

So it's basically just for looks, income and jobs?
That sucks. But at least it saves me the trouble of trying to make an efficient harbor.