What do roads do?
- Clearly point the way to where you want to go
- Clear obstacles (trees, undergrowth, bushes, rocks) from the way
- Easier walking surface (hard surface. Note the Incas didn't have horses or wheels, and often the roads where flights of steps up and down mountains. The principle still holds with asphalt surfaces better for driving on)
What roads don't do
- provide energy to actually move stuff (unlike the rail network)
- BruceSterling : I'm starting to suspect that the 21st century's got some kind of cool, unsuspected twist here, something like a Google page-ranking algorithm for highways and traffic lights. Imagine a kind of Slashdotting for traffic jams. Get visionary with me here.
See also :