Abstract: Use three etrrved square laws on one of the basic alignment's cnrvity line to fit a new alignment that is not only succession in curvity，but also even succession in rate changing of curvity，thus make the alignment pleasantly and drive a vekicle orbit in succession．In order to adapt to the high-speed security of driving．

Key words: basic alignment, three curved square laws, the rate of curvity is continual

摘要： 运用三弯矩法对基本型线形中的一种线形的曲率线进行线形拟合．使拟合线形不但曲率连续，而且曲率的变 化率也连续，从而使路线线形更加顺适、行车轨迹更为连续．以适应高速行车的安全．

关键词: 基本型线形, 三弯矩法, 曲率变化连续