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比较了现行中美规范平行式加速车道长度计算方法的差异,结合运动学模型和可接受间隙理论,在考虑主线交通水平、初始速度与可变间隙3种影响因素的基础上,建立了城市快速路平行式加速车道长度计算模型,采用蒙特卡洛方法求解模型,分析了3种影响因素对加速车道长度的影响,并提出了一种基于期望初始速度和期望主线交通水平的加速车道长度确定方法。分析结果表明:3种影响因素对加速车道长度有较大的影响,在不同设计时速下,《城市快速路设计规程》(CJJ129—2009)规定的长度最小值均小于仿真值,在设计时速为100km·h~(-1)时,三级服务水平上下限的加速车道长度分别比规定的最小值大27~36、9~27 m,在设计时速为80km·h-1时,分别大10~22、4~24m,在设计时速为60km·h~(-1)时,分别大15~24、13~30m;随着初始速度的减小,加速车道长度呈现增大趋势;在相同条件下,第4种临界间隙函数的加速车道长度最大,而第1种临界间隙函数的加速车道长度最小,表明临界间隙越大,需要的加速车道就越长;不同设计时速下三级服务水平上下限加速车道长度和初始速度的二次函数拟合度为0.865 8~0.999 7,因此,整体拟合效果良好。可见,本文的快速路平行式加速车道长度计算方法合理、可靠。
Based on the kinematics model and the theory of acceptable clearance, considering the influence factors of the main traffic level, the initial speed and the variable clearance, the rapid urban rapid Road parallel acceleration lane length calculation model, the Monte Carlo method is used to solve the model, the influence of three kinds of influencing factors on the acceleration lane length is analyzed, and an acceleration lane length determination method based on the expected initial speed and the expected main line traffic level is proposed . The results show that the three kinds of influencing factors have a great influence on the length of accelerating lanes. At different design speeds, the minimum length stipulated in Code for Design of Urban Expressway (CJJ129-2009) is less than the simulation value. When the designed speed is 100km · h -1, the acceleration lanes of the upper and lower service levels are 27 ~ 36,9 ~ 27 m above and below the prescribed minimum and at the designed speed of 80km · h-1, respectively, ~ 22,4 ~ 24m, respectively. When the design speed is 60km · h ~ (-1), they are 15 ~ 24 and 13 ~ 30m respectively. With the decrease of initial velocity, the length of accelerating lanes shows an increasing trend. Under the same conditions , The fourth type of critical gap function has the fastest acceleration lane length, while the first type of critical gap function has the smallest acceleration lane length, which means that the larger the critical clearance, the longer the required acceleration lane. The service level of three stages at different design speeds The quadratic function fit of the lower limit acceleration lane length to the initial speed is 0.865 8 ~ 0.999 7, so the overall fitting result is good. Obviously, this paper calculates the length of parallel expressway with reasonable speed and reliability.