Editing Railroad switch (section)

=== Switch diamond ===
[[File:Switchdiamond.jpg|thumb|A switch diamond at a junction in the UK]]

Although not strictly speaking a turnout, a ''switch diamond'' is an active trackwork assembly used where the crossing angle between two tracks is too shallow for totally passive trackwork: the unguided sections of each rail would overlap. These vaguely resemble two standard points assembled very closely toe-to-toe. These would also often utilize [[swingnose crossing]]s at the outer ends to ensure complete wheel support in the same way as provided on shallow angle turnouts. In North America these are known as ''movable-point diamonds''. In the UK, where the angle of divergence is shallower than 1 in 8 (center-line measure) a switched diamond will be found rather than a passive or fixed diamond.

Such switches are usually implemented on the basis of increasing the safe crossing speed. Open blades impose a speed restriction, due to the potential of the crossing impact fracturing the rail as both wheels on each axle hit the crossing gaps almost simultaneously. Switched blades, as shown in the photograph, allow a much higher speed across the gap by providing an essentially continuous piece of rail across the gap on both sides.

The frog end of the switched crossing, despite still having a gap in one rail, is less problematic in this regard. The outer rail is still continuous, the wing rail (the part that turns out, after the frog gap) provides a gradual transition, and the check rail avoids the possibility of points splitting. This can be seen in how, under examination, the wing rail has a wider polished section, showing how the wheel load is transferred across the gap.

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