Application-oriented electronics methods for detection of parking traffic jams simplify the control systems and increase the efficiency. This paper explores the possibility of traffic jam forecast. Main target of this paper is to show possibility to forecast traffic jam before it starts and not only detect it. This paper proposes jam forecasting and detection technology using set of traffic flow data. In this method, time series data of traffic flow events considered as a combination of frequency are transformed into several frequency data. Experimental researches were done in real parking lot in Kaunas. Created methods and structures of electronic flow control systems increase efficiency of traffic flow control sytems in the places of mass gatherings.