在目前互通立交平面线形设计过程中　直接式变速车道设计时　变速车道长度控制比较难　 目前尚没有通用的解算方法。
尤其是变速车道起点对应的主线线形为团曲线或缓和曲线时　往往反复试算调整　也难以得到比较理想的设计方案。 本文立足通
用的立交线形设计方法　提出一个以变速车道长度为收效条件的线形参数解算方法。(In the current interchange layout design, the control of speed lane length is rather difficult when designing the direct lane change lane, so there is no general solution.
Especially when the main line shape of the starting point of the speed change lane is a cluster curve or a transition curve, it is often difficult to get a more ideal design plan after repeated trial adjustment. This article has a foothold
A linear parameter calculation method based on the length of variable speed lanes is proposed in this paper.)