Operation reliability for on-ramp junction of urban freeway

A disorder situation of traffic operation always appears in on-ramp junction area of urban freeway, because the operation action for vehicles presents the weaving condition, especially for different vehicle types. Based on the analysis on the cellular automata theory, and combining with on-site survey data, several key parameters were defined, namely, cellular length, cellular speed, cellular acceleration, updating time interval. In addition, cellular acceleration rule, cellular deceleration rule, random rule, lane-changing rule and other micro-simulation rules were set, and cellular automaton micro-simulation model was set up. Further-more, a micro-simulation module was developed for traffic operation actions of on-ramp junction with Matlab toolbox. Finally, a simulation experiment for traffic operation reliability was done with this micro-simulation module, and the situation of change for on-ramp junction area was obtained under the conditions of different mainline design speed, acceleration lane length, vehicle generation probability and lane-changing probability. The results show that operation reliability for on-ramp junction is determined by the parameters of the probability of vehicle generation and the length of acceleration lane, especially for on-ramp.