BS EN 13803-2:2006 pdf download – Railway applications — Track — Track alignment design parameters — Track gauges 1435 mm and wider — Part 2: Switches and crossings and comparable alignment design situations with abrupt changes of curvature
NOTE A tolerance of 10 mm on the maximum limiting values is permitted for existing turnouts laid on lines to be upgraded for high-speed.
7.1.3 Plain line Plain line alignments with abrupt changes of cant deficiency shall only be used when the scope for designing the alignment is severely restricted. Such restrictions occur in stations, at small deviations in alignment within a limited length, or in compound curves when there is only a small variation in the radii of abutting curves. The recommended limiting values for abrupt change of cant deficiency on plain line shall be as specified in Table 3.
The use of higher values of abrupt change of cant deficiency should, if possible, be avoided. If the use of higher values is unavoidable, for example in close conjunction to switch and crossing layouts, the limiting values shall not exceed those specified in 7.1.2.
7.2 Limiting values based on the principle of the virtual transition Some European railway authorities use the principle of the virtual transition (see Annex E). The limits applicable for this principle are given in E.3.
7.3 Minimum radius of horizontal curves On all tracks (including the diverging tracks in switch and crossing layouts) where different railway vehicles operate, the designed minimum radius for any curve shall not be less than 150 m. In the case of a reverse curve, or curves in opposite directions with short intermediate elements, the alignment design shall conform to 8.4.
8 Combinations of horizontal curves
8.1 General Horizontal curves can be combined to form a reverse curve, curves in the opposite directions with an intermediate element, a compound curve, and curves in the same direction with an intermediate element. These types of situations are shown in Figure 2. The track elements may have constant curvature (as in Figure 2), but may also be transition curves (for a turnout placed on a transition curve and/or a turnout with variable curvature). In some cases the intermediate element may be a transition curve of sub-standard length, i.e. a transition curve that does not conform to the requirements of ENV 13803-1. In practice, such situations occur in:
the diverging tracks in switch and crossing layouts;
plain tracks abutting switch and crossing layouts;
plain tracks where it is impractical to provide full transition curves (typically stations and sidings);
plain track alignments with large radii curves;