| | | Sight is a very complex problem, involving different design variables: already existing constraints impose choices which, while satisfying the minimum parameters required by the policy according to dynamic dimensioning parameters (minimum planimetric radius), do not necessarily grant sight in curve, this being influenced also by the size and the geometry of the cross section and by the presence of obstacles (guard rails, walls, tunnel piers, etc). Therefore, an alignment respecting the dynamic geometric parameters required by the policy, does not necessarily grant sight distance; on the contrary, to comply with this test, it is necessary to perform further analysis, considering all the variables at the same time and then providing results. Sight diagram calculation ProSt A is the solution for testing the sight and generating the corresponding diagram; sight diagram reports on X axis the stations and on Y axis the stopping distance calculated according to the speeds taken from the corresponding speed diagram. This diagram then reports the sight distances verified; in this way, the areas | | where the stopping distance is above the sight distance, i.e. areas where sight is not granted, can be easily detected. The test can be performed by setting all the variables to be considered. For example, it is possible to set, in the same diagram, the stopping distances for different maximum speeds (to verify whether speed limit should be reduced in some segments) or the sight distance for different lanes (internal lane, external lane). For each sight distance to calculate many other parameters can be set, such as the height and the distance of the point of view, obstacle height and distance, colour, linetype, etc. Widening calculation ProSt A not only generates the diagram but can determine automatically the widening in curve that can grant the sight; such widening can be set directly on typical section shoulders so as to create automatically a project satisfying sight requirements. Road 3D model The sight distance, and the widening that can grant it, is calculated by using a 3D | | model of the road that is generated automatically according to alignment, vertical design (optional) as well as according to the typical section geometry and size. It is in fact possible to create a simplified typical section and specify such parameters as lane width, height and size of the obstacles(guard rails, new-jersey, walls, etc.) according to the alignment station. Generating a 3D model of the road is the only way to make sure that, for the sight test, all project parameters have been considered simultaneously. Determining sight distance can either be limited to the alignment or include also altimetric elements; if an only-planimetric test is performed, the model will be generated on a completely horizontal plane, while, if a plano-altimetric test is performed, the model elevations consider the altimetric design as well. Reports and drawings The final diagram can be customized with all kinds of dimensioning and can be printed directly on plotter/printer or exported in DXF/DWC format. | | |