Speed diagrams of rural roads are an essential tool for the good geometric road design, for the control, in existing roads, of the geometrical layout characteristics (visibility distances, coordination between successive elements, the climbing lane for the heavy vehicles). Again they can be used, with information to vehicle weights, to improve sizing of safety barriers. These operations can be successfully performed if it will increase the knowledge of the speed characteristics in road sections with greater accident risk. There are many studies realized on driver speed, in the last two decades; the resulting values and relationships are different from each other. Every Country has an its own relationship that characterizes the behavior of drivers in road environment: it is not possible to define a single formula for different situations and different drivers. In the paper, in particular, it describes an experimental relationship obtained of the distributions of running speeds of vehicles recorded, in significant periods of time, in different conditions of geometric path and different provinces. The surveys were conducted on various two-lane roads and have allowed to identify a good relationship for the dependence of the operating speed of the layout geometrical elements not only with the free flow speed (FFS, 85th-percentile) and the CCR (curvature change rate), but also with the road longitudinal gradient. It has used the measurements over 40 sections of rural roads with two-lane single carriageway, width greater than 7 meters, long straights and curvature radii greater than 100 meters. The roads are located in Italy, in the provinces of Grosseto, Caserta, Benevento, Cosenza and Naples, with different plan and elevation views of alignment. The environmental conditions of surveys have always been clear weather and daylight. The values obtained were interpolated with different relations and the results were compared with those obtained from other authors in the same geometric conditions.
SPEED DIAGRAMS: AN UPDATED RELATIONSHIP FOR V85
ABBONDATI, FRANCESCO;
2016-01-01
Abstract
Speed diagrams of rural roads are an essential tool for the good geometric road design, for the control, in existing roads, of the geometrical layout characteristics (visibility distances, coordination between successive elements, the climbing lane for the heavy vehicles). Again they can be used, with information to vehicle weights, to improve sizing of safety barriers. These operations can be successfully performed if it will increase the knowledge of the speed characteristics in road sections with greater accident risk. There are many studies realized on driver speed, in the last two decades; the resulting values and relationships are different from each other. Every Country has an its own relationship that characterizes the behavior of drivers in road environment: it is not possible to define a single formula for different situations and different drivers. In the paper, in particular, it describes an experimental relationship obtained of the distributions of running speeds of vehicles recorded, in significant periods of time, in different conditions of geometric path and different provinces. The surveys were conducted on various two-lane roads and have allowed to identify a good relationship for the dependence of the operating speed of the layout geometrical elements not only with the free flow speed (FFS, 85th-percentile) and the CCR (curvature change rate), but also with the road longitudinal gradient. It has used the measurements over 40 sections of rural roads with two-lane single carriageway, width greater than 7 meters, long straights and curvature radii greater than 100 meters. The roads are located in Italy, in the provinces of Grosseto, Caserta, Benevento, Cosenza and Naples, with different plan and elevation views of alignment. The environmental conditions of surveys have always been clear weather and daylight. The values obtained were interpolated with different relations and the results were compared with those obtained from other authors in the same geometric conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
