Secondary industry is particularly vulnerable to transportation difficulties, for the actual manufacturing process is often no more than a brief act of separation, synthesis or transformation preceded by the lengthy operation of assembling raw materials and fuel and followed by the distribution of the product to its multiple consumers. Economic secondary production consists very largely in the correct choice of a location which will minimize the combined costs of assembly and distribution, and is thus very dependent upon the availability, cost and effectiveness of the transportation system.
This problem is seen in its most striking form in countries such as Afghanistan, Bolivia, Lesotho and Nepal, where terrain reaches up to the highest mountains in the world and makes road construction extremely costly. In such places the high cost of construction is very slowly offset by the economic returns from villages which are set far apart, even though some may be situated in very fertile land, have fine stands of timber or possess other good natural resources. Another difficulty is that many developing countries cannot afford, and perhaps do not need, the sophisticated vehicles of Northern manufacture, although simpler, less expensive, locally designed and manufactured vehicles would also create a demand for adequate roads and highway networks. While developing nations have invested from 15 to 35% of their national budgets to transportation infrastructure, of which three-quarters was spent on roads the networks are only growing at a rate of 0.2 to 9.5% in length. The density of road networks in developing countries is only about 10% of developed countries.