Calibration and validation of and results from a micro-simulation model to explore drivers’ actual use of acceleration lanes

This study investigates the actual use of acceleration lanes by means of traffic micro-simulations in proximity to the convergence between the main and the secondary traffic streams. The data needed to develop the micro-simulation model were collected videotaping two acceleration lanes of an Italian highway, near the village of San Liberato. The relevant microsimulation model has been developed utilizing a commercial software, the TransModeler traffic simulation package, while the calibration and validation phases have been realized based on real-life data. Thanks to the microsimulation model, six different scenarios based on various presentation speeds have been analyzed, in a less expensive, quicker and more secure way compared to field observations. A quantitative and qualitative analysis of the results has been discussed to examine both geometric and kinematic aspects of the merging maneuvers and to compare road users’ behaviors with theoretical road design guidelines. The analyses have been focused on vehicles coming from the on-ramp, in terms of entrance points dispersion into the main traffic stream along the acceleration lanes, merging speeds, and reached acceleration rates. The mutual influence between the two flows (main and secondary traffic streams), combined with vehicle performances and characteristics of drivers, led to a first assessment of the main variables from which the required length of the specialized lanes depends.