A Method for Comparing Alternate Pavement Designs

Abstract

The purpose of this research was to develop a method for comparing a set of preselected pavement designs for a proposed section of state highway in Indiana. This comparison is based on consideration of both economic and performance requirements. The major portion of this study was devoted to obtaining a measure of the total performance of highway pavements with known design characteristics and traffic loadings. The AA3H0 Performance Equations determined in 1961 at Ottawa, Illinois were used to predict the present serviceability trends with time of 160 study pavement sections. A serviceability trend is a measure of the performance of a pavement. The AASHO equations were found to estimate the present serviceability of Indiana highways within acceptable limits of precision. However, additional precision was obtained by modifying these equations to reflect the lower initial serviceability levels of Indiana rigid, flexible, and overlay-pavements compared to the AASPiO Road Test pavements. The modification was accomplished by regression analyses between the predicted ix and measured present serviceabilities of the study sections. The regression equations have been termed the Indiana rigid, flexible, and overlay serviceability equations. From the Indiana equations, tables were compiled listing the anticipated performance of various pavement designs under a wide range of traffic loadings. The tables Included in this report permit determining the performance-to-cost ratio of each of the pavement designs to be compared. This ratio can be used to select the proper pavement design for given traffic and environmental conditions. When loadometer data are not available, the use of the AASHO and Indiana serviceability equations is facilitated by the technique developed in this study for approximating the number of equivalent 18-kip single axle load applications a pavement section has received. This estimate is made on the basis of the number of trucks traveling over the highway.

A Methodology for Evaluating the Impact of Railroad Abandonment on Rural Highways

“…The delineation of those highways in the 3-county study area which might be affected by railroad abandonment was accomplished primarily by using the results of the rail user survey conducted by this research effort. As stated previously in Chapter 11, (25).…”

“…User agencies in Indiana may determine the S-value based upon the results of a study conducted by Ulbricht in 1967 (25) .…”

“…The mean rating of this panel of soil experts was taken as the best estimate of the relative performance of a given soil type (25) To ascertain the soil support value for any highway facility within Indiana, the map entitled, "Engineering Soil Parent Material Areas of Indiana, JHRP , 1950," must be consulted. A copy of this map is reproduced as Figure 31 in Appendix C. By using this map in conjunction with Table 25, which contains S-values for each soil unit displayed on the map and is also located in Appendix C, a soil support value for the study section can be easily determined.…”

Sensitivity Analysis of Various Cost Elements in Flexible Pavement Design

“…The equation developed by Ulbricht (3) was used to arrive at the total cumulative number of equivalent 18-kip single axle applications in terms of average daily traffic.…”

“…These factors arc: (1) traffic on the section measured in vehicles per day for two lanes of pavement, (2) type of subgrade soil, (3) thickness of the surface, and (4) thickness of the base and/or subbase.…”