Avoiding instabilities in short gap car-followings with connected autonomous vehicles

Abstract

The image of driverless vehicles cruising on highways has been coming closer to reality over the last years thanks to the constant investigations in the technologies used in Connected and Automated Vehicles (CAV). Platooning of CAVs has been the focal point of investigations due to the potential benefits that can be reaped from the proper implementation of platoons on highways. One of the challenges facing the successful operation of platoons is the bullwhip phenomenon that causes propagating perturbations in platoons hindering its stability. The present study focuses on eliminating or reducing the bullwhip effect suffered by vehicles in a platoon. The aforementioned platoon algorithm will be governed by the formula of the Desired Space Gap (DSG) as followers will have to maintain a gap equal to the DSG to follow the leader. This algorithm managed to successfully carry out any increase or decrease in velocity of the platoon however, in the case of braking it has proved to be extremely unstable and suffers from effect of the bullwhip phenomenon. The average cumulative gap was used as a solution to trigger an instant response from all vehicles down the platoon to the actions of the leader as it was observed that vehicles in the end of the platoon tend to approach the leaders at high velocities because they only start decreasing their velocities once the vehicle ahead of them decelerates rather than the leader. This solution has been effective in significantly reducing the bullwhip effect on some vehicles in the platoon only, mainly the ones at the end of the platoon. Furthermore, this solution has given positive results only in cases of great changes in velocity.