Congestion on expressways has become a serious problem and causes serious economic loss. In particular, traffic congestion at sags, triggered by slow down of some cars in uphill sections have been major cause of natural traffic congestion. This paper proposes schemes to control lane change of cars through periodic control message broadcast from the roadside server to cars via road to vehicle communication. In this scheme, the type of lane change control and its parameters are adaptively changed depending on the amount of traffic flow in each lane measured in real-time by vehicle detectors. Lane change controls comprise probabilistic forced lane change which is applied before congestion occurs and lane change restriction which is applied during congestion. The results of traffic flow simulation show that proposed scheme reduces the travel time to pass an uphill section of sags with the configuration of control area considering behaviors of cars before and during congestion.