A behavioural model of flows on roundabouts

Digital simulation programs describe the reality with different levels of detail: models of territorial planning are essentially macroscopic (flow - variable), those for the design are microscopic (flow kinetic characteristic - variable). Study of the intersections requires models of this second kind. On roundabout, with at least two lanes, four are conditions of circulation: immission in flow, circulation on the ring with other vehicles, change of lane (to right or to left) and leaving intersection. Each of these conditions requires an interpretation model that must indicates what measurable greatness (speed, accelerations, gap, lag and so on) could link to drivers behaviour and what are variations of these for different flow conditions. Into intersection each driver is to operate successively in the four flow conditions shown. From this sequence is obtained the microsimulation model as link of partial submodels. As more they are accurate so many good the full program will work. For study the shown manoeuvrings has been realized a first survey on three different intersections with similar geometric characteristics, with different circulation conditions (variable flows) and with different drivers customs (the roundabouts are in two regions). The data acquisition, extraction and next analysis has furnished necessary indications to define some behavioural models. For available space in this paper is showed only an immission model: it have been tested and has given results in line with the surveys.