Effects of a slowdown warning system in mixed communication environments : A macroscopic study

Current ACC vehicles do not provide the driver with advance information of events occurring far ahead of him/her. In this paper, we discuss the concept of a slowdown warning system in automobiles, and analyze the same using PDE models. If a driver on a highway progresses abnormally slowly and/or generates large negative velocity gradients on the highway (thereby posing a hazard to the vehicles behind him/her), then, with such a system, the cars behind him/her are provided advance information of this. This advance information gives the drivers additional time to react, in anticipation of an impending slow-down, and this helps to smoothen the velocity gradients. Furthermore, and more importantly, it is seen that even if only a fraction of the cars in a platoon are equipped with such an advance warning system, this can still be sufficient to weaken the velocity gradients even in the unequipped cars. In this paper, we demonstrate this through simulations on PDE models assuming finite communication wave propagation speeds through the equipped cars.