Calibration of Speed-Density Relationships for Freeways in Aimsun

The first application of a calibration methodology which uses speed-density relationships in themicrosimulation calibration process is described in this article. Traffic patterns were implemented developingspeed-density relationships for empirical and simulated data. For empirical relationships reference was made totraffic data observed at A22 Freeway (Italy). Aimsun microscopic traffic simulator software was then used toobtain analogous relationships for a test freeway segment under uncongested traffic conditions. Thus on fieldconditions were reproduced varying some calibration parameters until a good matching between field andsimulation was achieved. The closeness between empirical data and simulation outputs was assessed through astatistical approach which included hypothesis testing and confidence intervals