This study focused on an in-depth examination of the driver behavior when driving through a curve on two-lane rural roads. Special attention was given to the lateral placement of the vehicles dependent on the optical impression of the curve and the roadside features, as well as on the general driving behavior, such as speed and acceleration/deceleration. In order to obtain the lateral placement of a vehicle passing through a curve a new method using video technique was developed at the Technical University of Dresden, Germany. This new aproach allows the exact determination of the lateral placement of a vehicle on every possible cross section of the curve. Consequently the calculation of the frequency distribution on spots of interest and the driven path of vehicles negotiating horizontal curves will be possible. It will be simple to define conflict areas, caused by critical encroachments of the centerline or the edgelines, detecting them on the computer screen and drawing by plots. This new developed method was applied on three curves with different horizontal and vertical geometric alinements as well as different roadside features. The results reveal that the driven path can be very different from the built curve radius, according to the variations in lateral placement as vehicles approach and traverse curves. A further result of the study is the fact that excessive speeds often caused critical driving maneuvers and consequently lead to conflict areas especially with the opposing traffic. One of the main issues of this study was also the development of quantitative safety factors to evaluate the safety level of curves depending on the driving behavior as well as on the geometrical and roadside features of the curves. These new developed procedure was also applied in a case study. (A)
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