Transportation improvements can have profound impacts on the areas they serve. A major highway improvement in the 1970s revolutionized the rural economy of Chilapa, a small town about 40 km east of Chilpancingo, the capital of Guerrero. Prior to 1970, the area was essentially self-sufficient, as it had been for hundreds of years. All the corn and most of food consumed in Chilapa came via pack animals from farms within 12 km of the town. It did produce some cotton shawls (rebozos) and later woven palm goods which were sold to obtain money for salt, iron, cotton, matches and other essentials not produced locally.
In the 1970s, the old narrow windy road to Chilpancingo was upgraded to a national highway (No. 92), straightened and paved, dramatically reducing transport time and costs. This had a dramatic impact on Chilapa. Corn and other goods from the rest of Mexico and abroad poured into the area, leading to significantly lower prices. The local farmers could not compete; many stopped farming altogether. Some started commuting by bus to low paying jobs in Chilpancingo. When subsidies became available for chemical fertilizers and hybrid corn, farmers began producing high quality corn that was sold outside the area. Chilapa continued importing cheap, low quality corn for local consumption. The new road completely changed the economy of the area around Chilapa, brought it farther into the national economy and improved its standard of living. There are thousands of communities in Mexico that are not yet served by paved roads and are essentially as self-sufficient and poor as Chilapa was before the 1970s. In addition, there are hundreds of other communities not reached even by dirt roads; they are even poorer and more self-sufficient.
Note: the main source for material about Chilapa is Kyle, C. 1997 “Transport and Communication” 1910-96, in Werner, M.S. (ed) Encyclopedia of Mexico: History, Society & Culture. Chicago, Fitzroy Dearborn.
The development of transportation systems in Mexico is the focus of chapter 17 of Geo-Mexico: the geography and dynamics of modern Mexico.