This study aimed at finding the effects of road geometry and cross-section variables on numbers of accidents. In addition, a methodology to combine variables by using decision trees was developed. Combination variables for road geometry and cross section were created by using the chi-square automatic interaction detection algorithm. Two negative binomial models were developed: one with homogeneous road segments and the other with 1-km road segments. Homogeneous road segments were divided on the basis of the horizontal alignment of the road. They were either curved or straight. The accuracy of the negative binomial model with homogeneous road segments was compared with that of the negative binomial model with 1-km road segments. The negative binomial model using homogeneous road segments was found to be the more accurate of the two models. The model with homogeneous road segments was used to draw conclusions with regard to the effect of variables on the number of accidents. Combination variables showed a significant effect on the number of accidents. The road geometry and cross-section variables were found to affect the number of accidents differently under various combinations of other variables.
Carbonized rice husk (CRH) and biochar (BC) were investigated as partial asphalt binder replacements. TCR and BC modified asphalt binders were initially evaluated with reference to their penetration index and then by volumetric properties, Marshall properties, indirect tensile strength, and moisture damage resistance of HMA made using a modified asphalt binder. Both BC and CRH modifications improved the high-temperature performance of the asphalt binder while reducing the actual asphalt binder required for the optimum HMA. A maximum of 13.75% reduction in actual binder requirement was observed. Although both modifications decreased the Marshall stability and Indirect tensile strength, at most of the modification levels the reductions were small. Marshall stability and Indirect tensile strength values were above the Asphalt institute specifications stipulated for heavy traffic (ESAL>10 6 for 20 years) highways. All modifications retained more than 80% of their Marshall stability and Indirect tensile strength when subjected to moisture conditioning.
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