Merging of tra?c ?ows is a potentially dangerous situation frequently associated with important impacts on tra?c ?uidity. This paper examines the possibility of improving merging from an entrance of a highway by adapting the speed of the incoming vehicles reducing as much as possible the need for actions by the drivers on the main lane. Multi-layer tra?c models are used to describe and simulate the interactions between drivers. A predictive controller is then designed to minimize the probability that the vehicles on the incoming roads need to change the speed or the lane. The proposed approach is shown to strongly enhance tra?c ?uidity for a wide range of tra?c densities on the main ?ow without compromising safety.