Driver Speed Behavior on Circular Curves of Undivided Two-Lane Rural Roads Serbian and Italian Case Studies

Many researchers have proved that one of the parameters that most influence safe driving is operating speed, defined as the speed at which drivers travel on a dry road in free-flow conditions during daylight hours. This study describes a comparison between driver speed behavior on horizontal circular curves located in Serbia and on circular curves located in Italy with analogous infrastructural geometric contexts. Only curves within a two-lane rural road network in low-volume conditions without spiral transition curves were studied. Operating speed profiles were plotted, and a careful analysis was carried out to study the deceleration and acceleration motion at each selected curve. Speed measurements were conducted by using different devices: (a) for the Italian case, laser detectors were used that emit and receive a pair of laser beams perpendicular to the road's axis and record the instantaneous vehicle speed and (b) for the Serbian case, sensors were used with an application software developed in the LabVIEW programming environment, and signals were logged in a binary file for which the vehicle speed was measured on the basis of the passing time between two consecutive sensors along the curve. Tvvo types of driver behavior were found: (a) deceleration when approaching the middle of the curve and acceleration leaving it and (b) deceleration over the whole circular curve length. A t-test was performed. Statistically, no significant difference was produced from the analysis when circular curves were located in different states that reflected the same geometric, traffic, and environmental context