Design approach of channelized island based on traffic conflict models at signalized intersection

In order to optimize the channelized island design at signalized intersection, a design approach of channelized island based on traffic conflict models was proposed. Traffic conflict data, traffic flow data, traffic control data, and geometric design data were collected at twenty signalized intersections in Kunming. Adopting Bayesian method, Bayesian fix parameter traffic conflict model and Bayesian random parameter traffic conflict model were constructed. The fitting goodnesses and significant influencing factors of the models were analyzed. Based on the random parameter traffic conflict model, the formula of calculating the expected number of traffic conflicts was determined. The design standard curves of channelized islands at signalized intersections were drawn, and the type selection procedure of channelized islands was proposed. Analysis result shows that the random parameter traffic conflict model yields better fitting result than the fixed parameter model. The variable coefficients of traffic volumes (crossing through traffic volume and right-turn traffic volume), channelized island types, and right-turn design elements (right-turn yielding sign and right-turn radius) obey normal distributions. When the crossing through traffic volume increases by 1%, the traffic conflict frequency increases by 0.56%. When the right-turn traffic volume increases by 1%, the traffic conflict frequency increases by 0.53%. The four types of channelized islands can reduce the traffic conflict frequency by 12.75%, 23.37%, 16.18% and 33.64%, respectively. The right-turn yielding sign can reduce the traffic conflict by 15.03%. When the right-turn radius increases by 1%, the right-turn traffic conflict frequency reduces by 1.72%. The research conclusion indicates that the design approach of channelized islands based on the traffic conflict models is feasible.