Cheapest Possible Road

A few years ago the "Cleveland Area Mountain Biking Association" and Geauga County Parks built a mountain bike trail at the park that adjoins my property. I've been a road cyclist/amateur racer since 1990, but never really got into MTB, because of the lack of trails. Now that there's a trail a mile from my house, I can ride over there in a few minutes and do a lap any time the trail is open, so I've been going a few times a week, weather permitting.

One of the things that's interesting to me about MTB is that people got very skilled at making trails over the years that there have been mountain bikes--really only about 40 years now. A small crew of volunteers, mainly, built and maintain about 6 miles of what's essentially a "road" through the woods. The trail contends with stream crossings, drainage, very steep climbs and descents without intensive use of materials.

The cost per mile is not zero, but it's probably as close as you could get to zero. It's not built for a practical purpose, so it twists and turns all over the place, climbs and descends needlessly, goes over bumps and jumps and difficult terrain on purpose to make the route interesting for riders and to pack 6 miles of trail into a 600 acre park. If it were built for practical transportation and utility, the path and approach would be somewhat different but it would be really usable. A person could get from A to B pretty easily over a $0 road.

The way "the system" works is apparent when you contemplate things like the transportation network. The transportation network tends to be completely replaced at each major iteration. For example, once there were trains, the canal and stagecoach era in northeast Ohio went away over the course of a couple of decades. In the car/truck era the trains routes collapsed to a minimal network.

A fairly large amount of the total production of "the system" is spent on the transportation network. The sub-components of the network all fit together. To use a certain tire composition, a certain wheel size, certain vehicle ground clearance implies a certain road surface, gradients, etc... All that leads to a certain cost per mile, which leads to a certain road density for a given population, and so on. This aggregate "solution" is arrived at incrementally over time and basically by accident, or via a process of mass trial and error. The solution is not optimal, plus the "optimal" scenario will change all the time.