Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.Includes bibliographical references (leaves 131-138).Recent news events and statistics demonstrate the frequent occurrence of pile-up crashes on highways. A predominant reason for the occurrence of such crashes is that current vehicles (including those equipped with an Automatic Cruise Control system) do not provide the driver with advance information of events occurring far ahead of him/her. The use of inter-vehicular communication to provide advance warnings to enhance automotive safety is therefore being actively discussed in the research community. In this thesis, we investigate scenarios wherein only a subset of the vehicles in a multi-vehicle stream, are equipped with such advance warning capabilities. These vehicles (equipped with the capability to receive far-ahead information) are arbitrarily distributed among other unequipped vehicles that are capable of receiving only local, near-neighbor information. It is seen that there are conditions wherein even a partial equipment of the system can be beneficial (to both the equipped and the unequipped vehicles in a mixed vehicle stream). We demonstrate this through both simulations and a theoretical analysis. Towards this end, two distinct modeling approaches are adopted: microscopic and macroscopic.(cont.) The microscopic modeling approach uses ordinary differential equations to model each driver-vehicle unit and its interactions with its neighbors. A single-lane model is employed; and the problem is formulated as a collision avoidance problem. Sufficient conditions on the number of equipped vehicles, as well as their distributions in a mixed vehicle string are obtained; under these conditions, it is guaranteed that collisions do not occur. The macroscopic modeling approach, on the other hand, uses partial differential equations that govern the average behavior of groups of vehicles. In this approach, a multi-lane formulation is employed. This thesis examines the influence of partial equipment of the advance warning system on some of the wave effects that are known to exist in traffic flows, in particular, shocks and large negative velocity gradient waves that travel unattenuated or get amplified as they pass through the traffic. We examine the influence of the equipped vehicles in attenuating such waves. The resulting velocity gradients are parametrized as a function of the percentage of equipped vehicles. A prototype of an advance warning system was also developed and road tests were conducted to test the concept. These road tests have demonstrated the system's performance to be satisfactory, subject to good communication links, for the class of scenarios tested.by Animesh Chakravarthy.Ph.D
