Built upon a seven-year local calibration study of Ontario’s flexible pavements, this paper provides a summary of the calibration results and design impact and, more importantly, shares the experience and lessons learned from the process. The best results have been achieved on the local calibration of the rutting, bottom-up fatigue cracking, and international roughness index (IRI) distress models minimizing the residual sum of squares (RSS) while maintaining the average bias at zero. Significant efforts have been made to calibrate the other distress models with limited success. A design impact study found that local calibration of the rutting models was very important, whereas the alligator fatigue cracking did not usually govern the design in Ontario, although the global model was found to under-predict the cracking damage. The performance of the calibrated IRI model in the design of heavy traffic freeways for both reconstructed and rehabilitated sections was unsatisfactory and needs further study. The paper also presents several open questions for future research. These include the handling of section-length effects of observed cracking data, the determination of initial IRI, the updating of standard deviation functions and the overall reliability models, and the prioritization of pavement research under the new paradigm of the Mechanistic–Empirical Pavement Design Guide (MEPDG).
The research used data from two-lane rural roads in Ontario, Canada to evaluate the change in safety following maintenance treatments to improve pavement condition as measured by International Roughness Index (IRI). The state-of-the-art empirical Bayes (EB) before-after methodology was applied to estimate the effects on crashes, separately for arterial and collector roads. The results indicate statistically significant reductions (P<0.05) in all crashes and property damage only (PDO) crashes of about 5% and 7%, respectively, for arterial roads and about 11% and 13% for collector roads. For fatal plus injury (FI) crashes, there were small, statistically insignificant changes for the two road types. The results provide interesting, and sometimes counterintuitive insights for those planning maintenance treatments to improve IRI. In sum, the results suggest that consideration should be given to designing and planning pavement maintenance treatments on a site-by-site basis, and, in so doing, to optimize the IRI levels and safety effects that may be accomplished with specific treatments.
The increasing need to rebuild and repair Ontario highways has motivated this research aimed at maximizing the efficiency of pavement maintenance and design. The first of two complementary objectives were to evaluate the safety improvements of reduced pavement roughness on two-lane undivided Ontario highways using the Empirical Bayes and Cross-Sectional analysis methods. The second objective was to improve the prediction of pavement distress and surface roughness by examining the impact of local calibration of prediction models. The findings suggest that better pavement conditions can reduce the severity of fatal and injury collisions by as much as 12% in some cases and therefore that pavement maintenance decisions should incorporate road safety when assessing cost-life analysis. The results provide a basis for those decisions in that they can be used to estimate the safety effect of a specific improvement in roughness.
The increasing need to rebuild and repair Ontario highways has motivated this research aimed at maximizing the efficiency of pavement maintenance and design. The first of two complementary objectives were to evaluate the safety improvements of reduced pavement roughness on two-lane undivided Ontario highways using the Empirical Bayes and Cross-Sectional analysis methods. The second objective was to improve the prediction of pavement distress and surface roughness by examining the impact of local calibration of prediction models. The findings suggest that better pavement conditions can reduce the severity of fatal and injury collisions by as much as 12% in some cases and therefore that pavement maintenance decisions should incorporate road safety when assessing cost-life analysis. The results provide a basis for those decisions in that they can be used to estimate the safety effect of a specific improvement in roughness.
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