Effects of combined curves on driver’s speed behavior: driving simulator study

摘要

The probability to occur in drive perception errors increases as the complexity of the road alignment increases. In particular\udperceptions errors could be significantly relevant in the conditions of horizontal curves overlapped with sag vertical curves (sag\udcombinations or combined curves). The highway geometric design guidelines of several Countries provide suggestions for the\udcoordination of the sag combinations in order to avoid combined configurations which can bring to undesirable optical effects\udand a reduced safety. Such suggestions come from studies based on the drawing of the perspective of the road. This drawing\udmethod is heavily limited with regards to the simulation of the perspective view of the highway to the driver during the dynamic\udtask of the driving. Interactive driving simulation methods are deemed to be more efficient for these aims.\udThis paper reports the results of a study carried out using an interactive driving simulator and aimed at evaluating the effects on\udthe driver’s speed behavior of different configurations of sag combinations and non-combined curves on flat grade with the same\udfeatures as the horizontal curves of the sag combinations (reference curves).\udThe main result was that on suggested sag combinations the driver’s speed behavior did not differ in any statistically significant\udway from that on the reference curves. Whereas the critical sag combinations (configurations that should be avoided) caused a\udhigh reduction in speed along the tangent–curve transition, which pointed the driver’s reaction to the wrong perception of the\udroad alignment This result, therefore, confirmed the effectiveness of the road design guidelines for the coordination of horizontal\udcurves and sag vertical curves.