On-Ramp Adaptive Traffic Volume in Freeway Merging Area

To implement on-ramp control and alleviate traffic bottleneck effectively in merging area, on-ramp adaptive traffic volume was researched considering the condition that time headway of different positions on mainline outer lane in merging area is subjected to different probability distributions. Firstly, traffic volume model of different positions on mainline outer lane in freeway merging area was analyzed. Then, by extending the correlative relationships between time headway distribution and traffic volume on mainline outer lane, the following results were obtained, when traffic volume is less than 378pcu/h, time headway is subjected to negative exponentially distribution, when traffic volume is in the range of 378–756pcu/h and 756–1134pcu/h, time headway is subjected to second-order and third-order Erlang distribution respectively. And then, applying gap acceptance theory and considering the three time headway distributions above, corresponding merging traffic volume models on different positions of the outer lane were developed. Lastly, according to the time headway distribution status on outer lane of mainline, on-ramp adaptive traffic volume model was established by means of piecewise integral. Research above indicates that on-ramp adaptive traffic volume in freeway merging area is a function of mainline traffic volume, ramp traffic volume, length of acceleration lane, critical gap and follow-up time. of merging vehicles, and interval status of vehicles' time headway distributions on mainline outer lane.