公路平曲线参数对车辆轨迹和速度的影响规律

为得到弯道几何参数对切弯时车辆轨迹和速度的影响,构建了切弯效用的量测指标———曲中速度增量和曲中轨迹半径增量,然后用"公路-驾驶人-车辆"仿真系统模拟了跟弯和切弯2种模式下的弯道行驶过程,得到了弯道转角、半径、路幅宽度、弯道长度与切弯效用之间的关系曲线,结果表明:①切弯效用在转角ΔA=20°时最大,然后随着ΔA增加而迅速衰减.②对于低于10°的小转角弯道,即使是跟弯行驶,轨迹半径仍大于弯道半径,只有ΔA>20°时,轨迹半径才会与弯道半径一致.③存在一个临界转角ΔA0C,当ΔA<ΔA0C时,路宽的增加才会提高切弯效用.④转角一定的情况下,切弯效用随弯道半径的增加而衰减,并且转角越大,衰减越迅速.⑤对于30m半径的急弯,不管路宽和转角取何值,切弯都可以提高通过速度.⑥切弯效用随弯道长度的增加而减小,弯道长度超过临界值时,切弯效用为零.

Effect of Horizontal Curves Design on Track and Speed of Passenger Car

To obtain the effect of change in design elements of curves on vehicle’ track and speed while driving in curve cutting,two indexes were established to measure cutting effectiveness,i.e.speed increment and track radii increment at mid-curve.Then,process of a car driving in curve cutting and lane keeping pattern on test curves was simulated by a "roadway-driver-vehicle" virtual driving system.And the relationships among curve radii R,deflection angle ΔA,roadway width WR,curve length Lh and cutting effectiveness were analyzed.The results show that cutting effectiveness reaches maximum at ΔA= 20deg,and it would decline as ΔA increase.For curves with ΔA less than 10deg,track radii in curve areas is larger than the curve radii even from lane following pattern.And only when ΔA exceeds 20deg,track radii can be in accordance with curve radii.There exists a critical angle ΔA0C,widening the pavement can result in an increase in cutting effectiveness only when ΔA <ΔA0C.Cutting effectiveness would decline as curve radii increase,and the larger ΔA,the faster in decline.For curves with 30 m radii,no matter how a ΔA and WR it has,an obvious speed increment can be gained by cutting.Cutting effectiveness would decrease as Lh increase,when Lh exceeds a critical length,the effectiveness being zero.