County highway needs identified in Iowa's Quadrennial Needs Study are used to determine the amount of funding allocated to each Iowa county for secondary highway improvements. The Iowa Department of Transportation uses a computer algorithm called HWYNEEDS to compute Iowa's secondary highway needs. Several highway operational, safety, and condition elements are collected and entered into HWYNEEDS. Variations in one of the condition elements, the pavement condition rating, were shown to significantly impact the resulting highway needs. Currently, pavement condition ratings are manually collected every ten years during the winter months. The Iowa Pavement Management Program (IPMP) provided a means to improve the condition ratings with improved data collection procedures. The IPMP uses an automated platform to collect pavement condition data at two-year intervals for the entire state during the year when pavement distresses are easier to recognize. A method was developed to compare the secondary highway needs resulting from the manual and automated collection procedures. First, a means to make the pavement condition data collected for the IPMP compatible with HWYNEEDS was needed. HWYNEEDS requires a pavement condition rating on a scale of one to five with five being a pavement showing no deterioration. As a result, the pavement condition data were converted to pavement condition ratings using equations developed through expert opinion. Second, a historical comparison of the highway needs derived from the manual and automated condition ratings was needed to indicate which data provided more consistent and accurate results. However, the IPMP was in its infancy; therefore, a historical database of condition data did not exist. As a result, pavement performance curves were developed for the automated condition data. Having created a historical database of automated condition ratings, the performance curves contained in HWYNEEDS were used to deteriorate the manual ratings. Pavement performance curves for both the automated and manual condition ratings allowed for more realistic comparisons of the data because the condition of the pavements could be deteriorated to common years. Finally, several data sets compiled from the automated and manual pavement condition ratings were entered into HWYNEEDS to compare the accuracy and consistency of the resulting highway needs.


  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 142-146

Subject/Index Terms

Filing Info

  • Accession Number: 00793286
  • Record Type: Publication
  • ISBN: 0965231046
  • Files: TRIS
  • Created Date: May 25 2000 12:00AM