D.I.T.S.: A Software for Sight Distance Verification and Optical Defectiveness Recognition

The visibility conditions assessment along a road alignments is made difficult by the continuous and uncorrelated variations of the parameters that describe the infrastructure and vehicle motion. The intrinsic computational burden is due to the calculus of these parameters in each verification point; the variables depend from the discretization of the road section. The paper proposes an assisted evaluation process for road alignments, related to the minimum stopping sight distance. Specific algorithms analyze safety conditions in every point of a discretized road alignment, comparing SSD (Stopping Sight Distance) and ASSD (Available Stopping Sight Distance). The aim is speeding up safety verifications, both for a new design or an existing road; in this way it is possible to improve design optimization process and to obtain an automatic control of standard specifications. Parameters like stopping and sight distances are calculated by a numerical integration of vehicle motion equations, through the use of theoretical Design Speed (Italian Standard) and/or Operating Speed. The last one is determined by means of literature models, especially the CCV (Continuous Speed Calculation) model: the results have been organized in a graphic interface of the proposed software D.I.T.S. (Integrity Diagnosis of Road Alignment). The D.I.T.S. allows to execute bi-dimensional and three-dimensional sight verifications on road alignments, considering both characteristics of infrastructure and environment. Moreover, it is possible to visualize dynamic perspectives, generated from the driver’s point of view. These representations provide the recognization and localization of errors or problems in the coordination of horizontal and vertical alignments and the optical deficiency depending on them. The verifications are also possible when the alignment is described by a simple series of points. Therefore it is not necessary to define the formal characteristics of geometric elements.