An example traffic control system includes a vehicle unit associated with a vehicle on a highway, one or more roadside units proximate the highway, and a traffic controller. The vehicle unit transmits a vehicle speed to the roadside unit, when in wireless communication range. The roadside unit transmits the vehicle speed to the traffic controller. The traffic controller receives vehicle speed data from a plurality of vehicles, and determines a suggested speed for each vehicle. The suggested speed may be correlated with an average speed of vehicles on a portion of the highway, for example the same highway portion on which vehicle is located, or a highway portion towards which the vehicle is heading.