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For increased accuracy of the results of the procedures in the Highway Safety Manual (HSM), states are encouraged to develop jurisdiction-specific safety performance functions (SPF), if necessary. After performing calibration of four-lane divided rural-multilane segments using the HSM methodology, underprediction was observed for total crashes and overprediction was identified for fatal and injury crashes, indicating a need to examine the development of local SPF for Kansas conditions. Accordingly, negative binomial regression was applied to obtain the most suitable model for local conditions. Several additional variables were considered and tested in the new SPFs, which were run through validation set of locations to confirm accuracy. The newly developed SPFs were also compared to the HSM-given SPF and adjusted SPF using statistical parameters such as mean prediction bias, mean absolute deviation, and mean squared prediction error, leading to the conclusion that the newly developed Kansas-specific SPF for four-lane divided rural highway segments reliably predicts total crashes and fatal and injury crashes in rural Kansas. The Kansas-specific SPFs are capable of more accurately predicting total crashes and fatal and injury crashes on multilane segments compared to the HSM and the modified HSM models. [ABSTRACT FROM AUTHOR]

Incorporation of high quantities of reclaimed asphalt pavement (RAP) in new asphalt pavement construction is a contemporary approach for promoting sustainable roadway systems. Many highway agencies, however, have reported premature cracking and raveling of hot-mix asphalt (HMA) pavements constructed with high RAP content. In this study, cracking resistance of HMA Superpave mixtures with 20-40% RAP from various sources was evaluated by conducting semicircular bending (SCB), Texas overlay (OT), dynamic modulus (DM), and simplified viscoelastic continuum damage (S-VECD) tests. Test outputs were analyzed using a full-factorial two-way analysis of variance (ANOVA) and Tukey's multiple comparison methods to quantify the effect of RAP quality and quantity on performance characteristics of Superpave mixtures. Although the SCB, OT, and S-VECD tests satisfactorily assessed cracking characteristics of HMA mixtures, results showed that the S-VECD test precisely captured the individual and combined effects of RAP source and RAP content. The DM test was unable to assess HMA mixture stiffness influenced by increased RAP contents or altered using various RAP sources due to the high error associated with the ANOVA model. [ABSTRACT FROM AUTHOR]