Legend Quest and Fletnern have the aldar. Though called dark elves (because they live underground), they are albino. They believe only in profits, so while they don’t consider themselves evil the ends will always justify the means - as long as the ends include profits. They hate the sun, so they need tunnels through which they can move their trade goods. So what do they do? They have firms whose job it is to tunnel through the continent. They prefer to use natural tunnels whenever possible, including widening the natural ones into trade routes. (We wanted to call them highways, but they are below ground, so ...) They send out scouts and spotters who find some good ways, and then they bring in the construction teams.
Standard (that’s a bad word, let’s say average) is 12’ wide with an arched ceiling with stone, support arches. The aldar employ slave diggers, mostly dwarves, trolls, and goblins, because those elven style arms just are not built for labor. Typically the engineers are aldar or dwarven, but they make use of mages and elementalists whenever possible to speed the work along. These tunnels travel hundreds of miles beneath the surface; these are major engineering feats. Currently they are connecting Forsbury to the rest of the network in order to make use of the surface trading giant.
This may seem useless, but think about it. First, underground there are no bandits - they control all access to the tunnels. Second, more often than not they go in reasonably straight lines. They don’t have to go around mountains or hills, though they will go deeper to get under water features. Lastly, since they built the tunnels, they are able to set the rest stops where they want them. They need to be built anyway, so they build them at exactly the right intervals. End result - these guys can move product faster than anyone else, safer than anyone else, and thus cheaper than anyone else. Do they lower their prices? Of course not! They just increase their profits.
For those of you gold farmers out there who only care about enhancing your damage numbers (though none of you are still reading this), you do care about this. You care because the aldar cartels make HUGE profits. Huge profits need to be protected. Huge profits cause rival cartels to go to war, and wars require mercenaries, highly paid mercenaries.