DESCRIPTION OF THE AUTOCORRELATION FUNCTION OF STEADY STATE SPEED PROCESSES

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THE AUTOCORRELATION FUNCTION OF LOCAL SPEED PROCESSES GIVES THE CORRELATION COEFFICIENTS FOR THE RELATION BETWEEN SPEEDS OF FOLLOWING VEHICLES DEPENDING ON THE NUMBER OF HEADWAYS BETWEEN THE VEHICLES. TWO VEHICLES FOLLOWING DIRECTLY ONE AFTER THE OTHER PROBABLY BELONG TO THE SAME COLUMN OF VEHICLES. THE GREATER THIS PROBABILITY IS, THE GREATER IS THE CORRELATION BETWEEN THEIR SPEEDS SINCE, ACCORDING TO THE DEFINITION OF A COLUMN OF VEHICLES, IT IS ASSUMED THAT RELATIONS BETWEEN THE SPEEDS OF FOLLOWING VEHICLES EXIST ONLY WITHIN COLUMNS. WITH AN INCREASING NUMBER OF HEADWAYS BETWEEN THE VEHICLES IT BECOMES LESS PROBABLE THAT BOTH VEHICLES BELONG TO THE SAME COLUMN. ASSOCIATED WITH THIS IS A DECREASE IN THE CORRELATION BETWEEN THE SPEEDS. THIS SHOWS THAT THE DISTRIBUTION OF COLUMN LENGTHS IS CLOSELY ASSOCIATED WITH THE COURSE OF THE AUTOCORRELATION FUNCTION. FOR THIS REASON, BY MEANS OF VARIOUS TRAFFIC FLOW MODELS AN ANALYTICAL STUDY IS TO BE MADE TO SEE WHETHER INFORMATION CAN BE OBTAINED ON THE OCCURRENCE OF COLUMNS BY MEANS OF THE AUTOCORRELATION FUNCTION.