文摘
Highway project delivery of new and reconstructed facilities in the United States is viewed to consume too much time,thereby denying the traveling public of urgently needed infrastructure. The purpose of this thesis is to gain a better understanding of current highway project delivery and suggest interventions intended to enhance time performance. The major research focus is the Highway Project Performance HPP) Study. The HPP study examined empirical data collected from 65 projects completed by 10 public highway agencies in the Northeast and Mid-Atlantic regions of the United States. Research included determining frequency and magnitude of duration escalation and identifying the input variables of process,practices,conditions,and constraints under which typical highway projects are delivered. Non-parametric procedures were used to test for differences among participating highway agencies. The Kruskal-Wallis and Mann-Whitney tests were employed to evaluate differences in mean TPI values for late and on time project subsets. Chi-square tests were conducted to analyze the difference in observations between the combined multi-dimensioned categories. Odds Ratio OR) and relative risk or the risk ratio RR) values were computed for the various categories including process and practices. Logistic regression was applied to the constraints as an additional test procedure. Semantic response differentials for each of the key performance indicators were also evaluated. The HPP Study findings showed that approximately 66% of highway projects finish beyond the original contract duration with a mean Time Performance Index TPI) of 0.859. Projects exposed to phased maintenance of traffic MOT),utilities,streams or waterways,and railroads exhibit the greatest relative risk for duration escalation. Primary arterials,projects that combine bridge and roadwork,and those located in urban environments also exhibit greater relative risk of duration escalation. The relative risk of duration escalation increases exponentially with increase of project cost. Late and On Time project subsets exhibit differences in mean semantic differentials MSD values) in constructability,the degree to which contract documents address constraints,quality and effectiveness of the contractors schedule,and trust between the contractor and owner. These findings provide focus and motivation for owners to reduce the risk of duration escalation.
