Risk analysis of ODOT’s HMA percent within limits (PWL) specification.

Details

• Creators:
  McTernan, William F. ; Cross, Stephen A.
• Corporate Creators:
  Oklahoma State University
• Corporate Contributors:
  Oklahoma. Dept. of Transportation. Planning & Research Division ; United States. Federal Highway Administration
• Subject/TRT Terms:
  HMA Hot Mix Asphalt Monte Carlo Method Monte Carlo Simulation Pavement Construction Paving Paving Materials Probability PWL Specifications Risk Analysis Road Construction Simulation Specifications Statistical Analysis

  More +
• Publication/ Report Number:
  FHWA/07(03)
• Resource Type:
  Tech Report
• Geographical Coverage:
  Oklahoma
• Edition:
  Final report.
• Corporate Publisher:
  Oklahoma. Dept of Transportation
• Abstract:
  The Oklahoma Department of Transportation (ODOT) is considering switching its method of payment
  
  for hot mix asphalt (HMA) construction from their current procedure to a Percent Within Limits (PWL)
  
  specification. Quality characteristics are percent asphalt content (%AC), percent laboratory compacted air
  
  voids (%AV) and percent roadway density (%RD). As the PWL methodology is new to both ODOT and
  
  its contractors, there is concern that differences between the methodologies could result in significant
  
  differences in the payments awarded for contracted HMA work.
  
  A risk based simulation approach, using Monte Carlo simulation, was structured to evaluate the
  
  probabilities that PWL’s generated randomly from a representative data base structured from ODOT
  
  paving projects would be within “acceptable” limits. In this way ODOT would be able to assess the
  
  expected performance and pay structure resulting from adoption of the PWL methodology against a set of
  
  previously collected data.
  
  The data set provided by ODOT showed that contractors are, on average, hitting the target value for
  
  asphalt content but running 0.37 and 0.9 percent below the target value for %AV and %RD, respectively.
  
  Comparisons of the ODOT generated data to data sets found in the literature indicate that the ODOT data
  
  set contains a high measure of control, while the simulation efforts showed that average performance for
  
  both %AC and %RD would earn bonuses but less than full pay for %AV, and less than full pay for the
  
  lot.
  
  The draft PWL specification as currently written appears to not fairly reward a contractor for a high
  
  level of quality control. Recommendations for adjustments in the target limits and specification limits
  
  were made. It is recommended that ODOT proceed slowly with the implementation of PWL
  
  specifications until a sufficiently large data base can be obtained and the analysis repeated to verify any
  
  changes to specification and target limits.
  
  
• Format:
  PDF
• Funding:
  Item 2182
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:6da71aa924e2a3ec69f04133c189dc97ebe3c3063678a4b2725cc95537d0e6a6
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24557/dot_24557_DS1.pdf
• File Type:
  [PDF - 608.17 KB ]