Why is a game about being a delivery boy so good? Is it the infrastructure building mechanic? Is it the batshit insane storyline? Is it the fact that every mountain is climbable? Is it the reserved use of combat and massive punishments for killing people?
Who knows, all I can say is I haven't had this much fun with a game in ages.
Zip lines people. Maintain your ziplines
You need most of them in the mountains, and have a pair for each moderately hard to reach area connecting it to a highway. That way you can pull up a truck and zip back and forth from the truck to the location until the order is finished.
I set them up so I could zip back and forth through the entire map, and it payed off incredibly well in the end.
Oh yeah, the ziplines feel like cheating sometimes. Especially when you have high bridge link and get other people's lines. Literally get to skip entire sections of the map.