Research On Applicability Of Right Turn Followed By U-turn Of Unsignalized Intersections On First-grade-highway

First-Grade-Highway, used to connect the cities, is fairly important parts in theentire highway networks. The principal function of the first-grade-highway is toprovide a safe travel environment and meet the demand of quick accessibility ofvehicles. Therefore, the road users usually require much better level of service offirst-grade-highway than other highways. However, it is found from previousresearches that intersections on first-grade-highway are the bottlenecks whichconstrain the functions of the first-grade-highway. Compared to the signalizedintersection, drivers’ behavior at unsignalized intersections becomes more disorderlydue to undefined right-of-way. Lots of previous researches revealed that using rightturn followed by U-turn instead of direct left turn could improve the safetyperformance of unsignalized intersections significantly. This paper compares andanalyzes two different kinds of right turns followed by U-turn at unsignalizedintersections of first-grade-highway in order to study their applicability undervarious road and traffic conditionsFirstly, this paper reviews the major applications of right turn followed byU-turn and concludes the current designs. For the actual road situations in China,two U-turn methods are finally determined which can be applicable to unsignalizedintersections of first-grade-highway in China, conventional U-turns andunconventional U-turns.Secondly, the simulation models subjected to direct-left-turn, conventionalU-turn and unconventional U-turn are established and analyzed through TSISsoftware. This paper shows that under different road situations, traffic flowcompositions and load of traffic flow, speed variance, average speed and averagevehicle delays in conflicting area may vary caused by varied types of U-turns. Basedon that, the U-turn applicable conditions can be decided from the respects of bothsafety and operational analysis.Finally, this paper concludes the research results and plans for the future work. The research achievements can serve as guides for domestic first-grade-highwayconstruction and renovation.