A method for determining traffic conditions includes: collecting real-time traffic information of a road; calculating a representative speed value for the road by a fuzzy inference, from the collected real-time traffic information and traffic condition factors having an effect on the road; and transmitting the representative speed value to a terminal of a vehicle traveling on the road corresponding to the representative speed value. The representative speed is sensibly determined and reliable information is supplied because the fuzzy inference's performance is based on the information collected from the signal transmitter and based on the factors which can affect the traffic conditions.