SIMULATION OF THE MERGING PROCESS

A MODEL IS PRESENTED WHICH SIMULATES THE MERGING OF TRAFFIC AT A FREEWAY ENTRANCE RAMP. MONTE CARLO TECHNIQUES ARE USED ON A DIGITAL COMPUTER TO GENERATE THE REQUIRED PROBABILITY DISTRIBUTIONS. THE TRAFFIC STREAMS ARE ASSUMED TO CONSIST OF PLATOONS SEPARATED BY RAREFACTIONS. THIS IS ACHIEVED IN THE MODEL BY ASSUMING A MARKOV RENEWAL PROCESS WITH TWO GROUPS OF STATES. THE FIRST GROUP IS A CAR-FOLLOWING GROUP WHICH GENERATES PLATOONS, AND THE SECOND GROUP IS A NON-FOLLOWING GROUP WHICH GENERATES THE MORE WIDELY SPACED TRAFFIC BETWEEN PLATOONS. THE TANNER-MILLER MODEL OF DRIVERS WITH CONSISTENT CRITICAL GAPS IS ASSUMED FOR GAP ACCEPTANCE WITH A LOG-NORMAL DISTRIBUTION OVER THE DRIVERS. THE MERGING STRATEGY IS SUCH THAT THE RAMP DRIVER DRIVES ALONG THE RAMP EXAMINING A LAG AND THEN A SERIES OF GAPS IN THE FREEWAY KERB LANE. WHEN HE FINDS A GAP GREATER OR EQUAL TO HIS CRITICAL GAP HE ACCELERATES AND MERGES INTO THE FREEWAY KERB LANE. RAMP DRIVERS ARE TREATED ON A FIRST COME FIRST SERVED BASIS SO THAT THE DRIVER IN FRONT MUST MERGE OR COME TO A STOP BEFORE THE NEXT DRIVER IS ALLOWED TO SEARCH FOR A GAP. THE MODEL IS ABLE TO PREDICT THE PROBABILITY THAT FOR A GIVEN VOLUME A DRIVER WILL BE UNABLE TO MERGE WITHIN A GIVEN DISTANCE. IT IS SHOWN THAT THE MODEL IS CAPABLE OF PRODUCING RESULTS WHICH ARE CONSISTENT WITH OBSERVED BEHAVIOUR. IT IS ALSO SHOWN HOW THE MODEL CAN AID THE PRACTISING ENGINEER IN DESIGNING A FREEWAY RAMP SYSTEM. /AUTHOR/