Farm to market. If you had asked what are rural roads used for 100 years ago the answer was simple. Farm to market. Farmers needed to get commodities to cities and towns and to connect with transportation systems which were mainly the railroads and the use of waterways from canals, rivers to ocean ports.
City folk didn't have much need to drive between cities, first, if they did, they would simply take the train, but realistically there were no roads to take them anywhere they may have wanted to go.
Fast forward to today. We can pretty much drive to anywhere we want to go. While the interstate highway system allowed us to connect across the country and infrastructure money was used to build these freeways that moved the country forward, little was done for the rural user. Federal dollars poured into states to build up their major highways between cities, pay for city streets and traffic control devices. Transportation moved forward. However, the rural roads that connected the farmer to the cities received scant attention and since most of them were owned by counties or parishes, they received little attention.
Some estimates are that rural roads have a 3 times higher accident rate than all other roads. Recently Map-21 eliminated the High Risk Rural Road program in an effort to streamline funding and may eliminate Federal dollars being targeted to the rural road system.
The problem will only be getting worse. The changing demographics that characterizes the urban/rural interface has not been well researched and not the result is it is not well planned.
A recent article in Transport Topics highlighted the increasing crashes in the Bakken Oil Fields of North Dakota including the number of fatal accidents that jumped from 9 fatal accidents in 2010 to 54 in 2013.
Rural "ain't" rural anymore!