Section 5: Pavement Type SelectionAnchor: #i1025362
Selecting a pavement type is an important decision. Like other aspects of pavement design, the 1993 American Association of State Highway and Transportation Officials (AASHTO) Guide states, “The selection of pavement type is not an exact science but one in which the highway engineer must make a judgment on many varying factors. . . ."Anchor: #i1025410
5.2 Principal Factors
The principal factors to consider in the selection process are:
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- Traffic Anchor: #ICRVLKWO
- Soils characteristics Anchor: #ASYNSREA
- Weather Anchor: #CVXBPYFU
- Construction considerations Anchor: #TRJNVGAS
- Recycling opportunities Anchor: #XBIGOIQV
- Cost comparison.
5.3 Secondary Factors
The secondary factors to consider in the selection process are:
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- Performance of similar pavements in the area Anchor: #XLWBOPCX
- Adjacent existing pavements Anchor: #RVTXUVRE
- Conservation of materials and energy Anchor: #VRCRJMBB
- Availability of local materials or contractor capabilities Anchor: #RMBICEXL
- Traffic safety Anchor: #MLMOHBNJ
- Incorporation of experimental features Anchor: #DSDVSFAL
- Stimulation of competition Anchor: #MGGFRUWF
- Municipal preference, participating of local government preference.
The decision factors considered for pavement design type shall be included in the pavement design report.Anchor: #i1008659
5.4 Life-cycle Cost Analysis (LCCA)
LCCA is an engineering economic analysis that allows engineers to quantify the differential costs of alternative investment options for a given project. LCCA can be used to compare alternate pavement types (flexible versus rigid) on new construction projects and rehabilitation projects. LCCA considers all agency expenditures throughout the life of the facility, not just the initial investment, and allows for cost comparison of options with varying design lives and potentially differing user costs to be compared on an equivalent basis.
More than a simple cost comparison, LCCA offers methods to determine and demonstrate the economic merits of the selected alternative in an analytical and fact-based manner. LCCA helps engineers answer questions like:
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- Which design alternative results in the lowest total cost to the agency over the life of the project? Anchor: #OXKBMCPS
- To what level of detail have the alternatives been investigated? Anchor: #JXJKWIDK
- What are the user-cost impacts of alternative strategies?
LCCA’s structured methodology provides the information and documentation necessary for successful open dialogue. Because of this, LCCA is a valuable analysis to support pavement type selection decisions.
The Federal Highway Administration (FHWA) has developed general guidance for running a detailed life-cycle cost analysis using RealCost. This website is a good starting point for information on running a life-cycle cost comparison of alternatives.
LCCA is only one of many processes for selecting a pavement type. The reliability of output from any LCCA is a function of the reliability of the input data and will be highly dependent upon the selected type and frequency of post-initial construction activities that extend the pavement service life to the end of the selected analysis period. It may be beneficial to evaluate user costs separately from agency costs when looking at different structural options.