Comparative analysis of straight-curve connection road section K-curve and clothoid
In order to comprehensively compare the differences between clothoid and K-curve in straight-curve connection road sections from multiple dimensions,the dynamic differences was analyzed of K-curve and clothoid in three freedom degrees(lateral motion,tilt motion,and yaw motion).The feasibility of K-curve as transition curves was studied,while examining the vehicle's driving stability on straight-curve connection road sections based on K-curve.By leveraging the characteristics of the K-curve heading angle,differential and analytical geometry approaches was used to validate the states of curvature and curvature change rate for both the K-curve and the clothoid.Using the dynamics software CarSim,simulations were conducted on five road models based on different design speeds.Vehicle lateral acceleration,vehicle roll angle,vehicle yaw angle,and steering wheel angle were selected as evaluation criteria.The differences in vehicle stability and driver comfort were analyzed,when driving on straight-to-curve transition road segments connected by two different types of transition curves.The entropy method was employed to assign weights to each indicator,and a comprehensive comparison was made between the advantages and disadvantages of the straight-to-curve road segments connected by K-curves and clothoid.The results show that the K-curves exhibit the advantages of continuous curvature and curvature change rate.Under the same design criteria,all stability parameters of vehicles on K-curves meet the demand of Design Specification for Highway Alignment(JTG D20-2017)and outperform clothoid.As the design speed decreases,the differences between K-curves and clothoid become more pronounced,highlighting the superior performance of K-curves in terms of vehicle stability and comfort.The study proved that under the same design speed conditions,K-curves exhibit overall superiority in driving stability,and driver comfort compared to clothoid.Particularly at lower design speeds,the advantages of K-curves become more pronounced.Therefore,K-curves can be effectively applied in the design of road alignments with lower design speeds to ensure and enhance road travel stability and comfort.4 tabs,8 figs,28 refs.