SAFETY MODULE FOR HIGHWAY GEOMETRIC DESIGN

Three safety criteria for evaluating curved roadway sections including transition sections were analyzed in order to address these important target areas for reducing accident frequency and severity. These criteria are (a) achieving consistency between successive design elements ; (b) harmonizing design speed and operating speed, especially on wet pavements ; and (c) providing adequate dynamic safety of driving. The above safety criteria constitute the core of the overall safety module proposed in this study for classifying road networks or roadway sections (or both), existing or planned, as good, fair, or poor designs. The evaluation process of the safety module, encompassing separate evaluation processes for each of the above safety criteria as well as for the combination of all three criteria, can be done manually by using the Geographic Information System known as SPANS. By using discriminating colors or symbols with SPANS, the resulting separate or combined design safety levels can be easily recognized by the highway engineer. For the case study in this paper, the actual accident rates for the majority of the investigated roadway sections corresponded with the results of the overall safety module, or the results were at least on the safe side. Generally speaking, the results in this paper appear to be pointing in the right direction for evaluating roadway sections and networks using various safety criteria. The proposed procedure verifies for the first time that the evaluation of roadway sections or networks by an overall safety module is possible for design, redesign, rehabilitation, and restoration strategies.