This is from the Sandbox.
Star Wars fans, picture a setting like the forest moon of Endor, albeit planet-sized and without Ewoks running about. For everyone else: Imagine a dense deciduous forest, with trees packed close together, stretching across the entire planet. The planet itself is Earth-like, and has Earth-like vegetation, trees, and forest creatures.
The main creatures are, for all intents and purposes, humans. They'll actually be humanoid, and not exactly human, but they won't have any major differences that will impact this question. They dwell in large treehouses, built in the mid- to upper- layers of the trees. The houses are accessible via rope ladders from the ground, although many are able to climb the trees outright. Tree-to-tree travel is made possible through rope bridges, though the more nimble can walk form branch to branch, making short jumps along the way.
How would transportation develop in such a world? I do have one idea: small, one-person gliders that fold up and can be carried. They can help when getting from one tree to another where there aren't any branches or bridges. They're used more often when traveling from the canopy layer to somewhere closer to ground level.
- The rope bridges can't hold any substantial weight.
- The materials at hand are all that can be found in a forest: Wood and some rock, as well as leaves, branches, etc. (The gliders are made out of sticks and animal skins, by the way, so any animal-based vehicles are also on the table.)
- There is no electricity use, but there are metals available, primarily iron. They are able to primitively produce iron.
- The plants (and some animals) here are those found in a deciduous forest.
The trees are close enough that it's impossible for any vehicles larger than a small car (e.g. a Mini Cooper) to feasibly go through.
Thanks to everyone for the comments and answers. I've thought a lot about the various suggestions over the past few days, and I've realized that no one method is going to be enough. I've decided on a combination of methods:
- The canals created by Abulafia and the boats discussed by Bill Blondeau
- The mini-airships suggested by ninesided (for small loads of freight, I think)
- The rope/ziplines invented by ckersch (and the resultant industry of rope-making)
and, as a plot device to lead up to a conflict . . .
- The burning of a small part of the trees, as suggested by Pavel Janicek
This is what I love about Worldbuilding - collaborative ideas always morph into something I could never have dreamed of.