Rural roads consist of local roads whose primary function is to provide
access to adjacent properties and arterial routes. As described here,
rural roads are low car and light truck traffic with some bus, heavy truck and
local farm traffic. Speeds vary but in many locations they can approach
highway speeds.
Figure 1: Rural Road in Grandview
Assumed Traffic
Low to high speed, low traffic volume and some heavy loadings. Heavy truck
traffic is usually limited to those involved with local services and delivery or
farm machinery.
Design Considerations
Rural road loading can vary widely. Roads that are part of bus routes or
are commonly used by heavy trucks (such as roads next to a gravel quarry) should
be designed using an approved procedure.
Construction Considerations
Rural roads are often been built on minimally prepared subgrade, which can lead
to subgrade failure resulting in
fatigue cracking and
depressions (see Figures 1
and 2). Special attention should be paid to questionable subgrade areas
and nearby fill embankments than may erode causing an edge depression or
failure. A construction geotextile can be used to help stabilize roadways
with early signs of subgrade failure or extensive cracking. However,
extensive subgrade distress cannot be solved by geotextile application.
Figures 2 and 3: Roads Showing Deterioration Because of
a Lack of Subgrade Support on the Edges
Recommended References
American Association of State Highway and Transportation
Officials (AASHTO).(1993).AASHTO Guide for Design of Pavement
Structures.American Association of
State Highway and Transportation Officials.Washington, D.C.
(www.aashto.org)
The Asphalt Institute. (1999).
Thickness Design - Asphalt, Manual Series No. 1. The Asphalt
Institute. Lexington, KY. (www.asphaltinstitute.org)
National Asphalt Pavement Association (NAPA). (2001). HMA
Pavement Mix Type Selection Guide, Information Series 128. National
Asphalt Pavement Association. Landham, MD.
(www.hotmix.org)
Recommended Minimum Pavement Thickness and Design
(inches)
