1.Method to determine the change of

1.Method to determine the change of distance between centers of lines1.The widening of distance between centers of lines in bridges or tunnels shall be completed in curves areas at the two ends of stations. In the case of difficult conditions, it can be completed on a straight line by using reverse curves.2.For railway lines of mixed freight and passenger traffic, if the change of distance is realized with a pair of reverse curves, if the minimum distance is limited by the minimum length if circular arc, it is not necessary to lay out a spiral at the two ends of circular curve. However, in these cases, the radius should be no less than the corresponding value in Table 3.7.3.For railway of mixed freight and passengers, if the change of distance is realized by using inverse curves, when the angle of deflection limit shall not meet the requirements of the maximum radius, the speed for passenger train is less than 100 km/h, and the minimum length of the spiral is 20 mm.2.Calculation of distance between centers on sections with change of distance1.In a straight track, according to the distance between centers of line, the change of curve can be calculated by using linear interpolation.2.At curve sections with change of distance, the distance between two lines can be calculated with special plane curve calculation method, using trigonometric analysis.