The utility model relates to a traffic safety technical field, concretely relates to highway trackside early warning device. The utility model provides a prevention highway vehicle rear -end collision, the highway trackside early warning device who exceeds the speed limit, this trackside early warning device is mainly by detecting element, communication unit, a main control unit, the early warning unit, memory cell, functional unit such as electrical unit constitute, the main realization is detected highway operation vehicle velocity, traffic flow operation parameter extraction, vehicle operation safety condition assessment and early warning, highway road running state monitoring etc, prevent highway vehicle rear -end collision, when exceeding the speed limit, for carrying out highway operation condition monitoring, the highway administrator provides the data support.