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26 values had similar magnitudes, and all were slightly smaller considered acceptable. For divided highways, the presence of than those obtained with the all crashes model. For the multi- left-turn lanes provided different results depending on the vehicle crashes, only presence of median barrier and shoul- crash type. For single-vehicle crashes, it showed an intuitive der width entered the model, and they had values similar result indicating that its presence has a benefit (AMF of 0.72). to those observed before. This was also the case for the all For multi-vehicle crashes, it showed an increase in crashes crashes model. (AMF of 1.57). This could be attributed to two possible issues: (1) the presence of higher operating speeds on divided rural highways and (2) the sites may not be truly rural sites, but are Summary within a more built-up environment. These explanations, The AMFs presented here follow the general trends of prior while plausible, cannot be verified with the available data, and knowledge and research. In general, the trends of the variables so they cannot conclusively explain the counterintuitive nature used in all models showed an agreement with rational expec- of the results. tations indicating reasonable trends. A notable result was A more critical issue with the AMFs developed in this for divided highways where there was an increase in crashes research is their magnitude and whether such significant dif- (all three models) with the presence of a median barrier. This ferences should be observed from the introduction or change could be associated with the possible higher speeds that could of each of these elements. This issue was addressed by a meet- be present on divided highways and, thus, the presence of the ing of the research team at which a reasonable magnitude was barrier could contribute to the occurrence of a crash. More- estimated by consensus for each selected design element. This over, the fact that an obstacle is placed within the roadway approach allowed the research team to consider past research, environment is an indication of the potential increase in crashes weigh the findings of this research, and adjust the magni- since the absence of any barrier could have resulted in an tude of the AMFs as needed to reflect practical and research unreported crash (i.e., the vehicle could have been able to experience. This approach also facilitated the development of return to the roadway and drive off). Therefore, this trend was the guidelines based on the research results.