Driver Speed Behavior on Circular Curves of Undivided Two-Lane Rural Roads

Many researches have proved that one of the parameters that most influence the safe driving is the 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 the driver speed behavior on horizontal circular curves located in Serbia and the driver speed behavior on circular curves located in Italy with analogous infrastructural-geometric contexts. Only curves falling within two-lane rural roads network in low-volume conditions without spiral transition curves have been studied. Operating speed profiles were plotted and a careful analysis was carried out to study the deceleration/acceleration motion at each selected curve. Speed measurements were conducted by using different devices: a) for Italian case, laser detectors were used that emit and receive a pair of laser beams perpendicularly to the road’s axis and they record the instantaneous vehicle speed; b) for Serbian case, sensors were used with an applicant software developed in the LabVIEW programming environment and signals logged in a binary file for which the vehicle speed is measured on basis of the passing time between two consecutive sensors along the curve. Two driver behavior types were found: a) drivers that decelerate approaching the middle of the curve and accelerate leaving it; b) drivers that decelerate on the whole circular curve length. T-test was performed. Statistically, no significant difference was produced from the analysis when circular curves are located in different states which reflect the same geometric, traffic and environmental context.