My pursuit of information about this topic has yielded less information than I would like. It seems intuitive, though – if our population continues to grow there must be a point where sufficient infrastructure either can’t be produced, or existing infrastructure can’t be sufficiently maintained. I will update this item as I find more information.
Will our ability to sustain our highways will reveal our status with regard to sustainability and overpopulation? Many in North America believe our current population is sustainable, as the birthrate is low compared with that of many other countries, but the highways we travel daily could reveal our true status. If sheer population doesn’t exceed our capacity to maintain our highways, fossil fuel shortages will make it so. Is there somewhere an intersection of the curves where the cost of maintaining existing infrastructure exceeds the tax revenues that support it?
Both short and long term views suggest overpopulation is a problem, even in the United States. Severe degradation of the infrastructure could happen in the short term as the economy sags under the burden of increasing fuel costs, thereby reducing tax revenues. In the long term this could occur as population stabilizes and declines worldwide. The short term situation may not be far off in North America, where major highways seem to be decaying through insufficient maintenance and major bridges seem to be at risk or even failing (like the I-35 bridge in Minneapolis (link). It is basic fact that the cost of maintaining any item of infrastructure will go on and on unless the infrastructure is abandoned, while the cost of new construction (admittedly also increasing) stops when the new facilities are opened for use. By that principle alone, funds available for new construction should decline relatively unless tax and other supporting revenues can keep up, which has seemed more doubtful as energy prices rise and begin to drag down the U.S. economy (and others).
Ancient road-building societies never reached the dense populations we have today. The Romans and Incas may have had a better understanding of such things than we do today – their roads appear to have lasted a lot longer than ours are (including after the empire that built and maintained them fell apart). They took centuries to build a lot fewer miles of roads than we have built in a handful of decades, and didn’t have vehicles with the numbers, weight, or speed we do. While they built and maintained their roads with human and animal labor, we have been doing it with the input of a lot of fossil fuel energy, a non-renewable resource we are already beginning to exhaust, as evidenced by rising prices. We are definitely building a great deal more infrastructure than they did, but we have a world population that can be estimated at twenty times that of the world in 1 B.C. (link). Also, we are far more mobile and use far more energy and other resources per person than our predecessors of centuries or millennia ago.
Studies I have found relating to highway infrastructure construction, renovation, and maintenance costs were all locally or regionally focused, and I am discouraged by my ability (so far) to find scholarly papers taking a broader approach to the topic. In any case, I will continue to research this topic from time to time, and will write on it again when I feel I have sufficient new information.
As always, I welcome your comments. – Tim
Report Card for America’s Infrastructure, the American Society of Civil Engineers