Perspective of Mitigating Shock Waves by Temporary In-Vehicle Dynamic Speed Control

This paper describes how shock waves can be defined as upstream moving traffic jams on motorways that may remain unchanged in size for a long time. Suppression of such jams by speed limit control has been investigated before with good results. The basic idea is to decrease the inflow to the jammed area, by reducing the traffic speed in upstream segments of the road. The approach until now was to assume that the speed limits are communicated to drivers by variable speed limit (VSL) signs. Current developments of in-vehicle driving assistance systems, especially of speed assistance systems would enable a different approach. Speed assistance systems focus primarily of information and warning, although it has been suggested that in a hybrid layout such systems might assume vehicle control mode where desirable, e.g. in situations with mixed traffic of motor vehicles and vulnerable road users. Such temporary control could also be used to more directly, precisely and homogeneously adapt the traffic speed to the calculated values for shock wave suppression on motorways. This paper studies the feasibility of this scenario, in comparison scenarios using communication by VSL signs. The scenarios are modelled using an adapted version of the macroscopic simulation model METANET, and model predictive control (MPC) for optimal coordination of speed limits.