Abstract
This research evaluated the influence of road geometric attributes on crash frequency. Survey data of the route was collected and used to design the 15km road using AutoCAD civil 3D. This design is according to the judgment of the survey team in terms of alignment according to the route conditions; and serves as the control for the study. The geometry of the design was altered by increasing the curves' radii by 15 and 30m to yield alternative design options 2 and 3 respectively. AutoCAD resets other geometric elements such as superelevation and slopes that best fit the new radii. The three design versions are modeled in AIMSUN NEXT for microsimulation of their traffic dynamics. Trajectories of traffic for each designed road corridor were collected and analyzed in the Surrogate Safety Assessment Model (SSAM) crash assessment for each. Increasing the curve radius from 135m (specified by the software) to 150m and 165m for options 2 and 3 respectively. Increasing the radius by 15m on the average for curves has eliminated some of the curves by integrating some closely spaced ones into some single and much more decent curves. Cord lengths for the resulting new curves were also elongated by this action. There is a fall in total conflicts from 2,682 in design option 1 to 1,688 in option 2. An additional increase in average curve radii in option 2 from 150 to 165m to yield option 3 roadway geometry yielded a much greater decrease in conflicts from 1,688 to 34 in options 2 and 3 respectively. Microsimulation and Surrogate safety assessment demonstrated prospects for crash predictions and mitigation and are applicable for both the operation and planning of road transportation systems.
Keywords: roadway geometry, traffic conflicts, AutoCAD Civil 3D, AIMSUN NEXT, SSAM, Trajectories
Key words: Keywords: roadway geometry, traffic conflicts, AutoCAD Civil 3D, AIMSUN NEXT, SSAM, Trajectories
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