一、引言我国铁路正线当前大量铺设的12号单开道岔,系1957年定型,并在1962年正式制订标准。对50、43、38三种轨型的道岔采用通用的平面尺寸,后在生产过程中进行了一些道岔结构方面的修改,且于1975年重颁部标准。现有标准12号道岔的容许通过速度:侧向,不分轨型一律规定为45公里/小时,由平面几何参数控制;而直向未作明确规定,在实际运营 I. INTRODUCTION At present, the No. 12 single-turnout currently laid on the main line of China’s railways is formally shaped in 1957 and formally formulated in 1962. On the 50,43,38 three kinds of railroad turnouts using a common plane size, after the process of making some changes in the structure of the turnout, and re-issued in 1975 ministries standards. The allowable speed of the existing standard 12 turnout: Lateral, irrespective of rail type are all set at 45 km / h, controlled by plane geometry parameters; while the straight direction is not clearly defined, in the actual operation