Transition types

The software supports the following transition types.

Method	Length	End station	PI
Clothoid spiral	*	*	*
Egg‑shaped clothoid spiral	*	*	–
Cubic spiral	*	*	*
Bloss spiral	*	*	*
Korean cubic parabola	*	*	*
NSW cubic parabola	*	*	–

Clothoid spiral

The clothoid spiral is defined by the length of the spiral and the radius of the adjoining arc. The formulae for the x and y parameters in terms of these two values are as follows:

Parameter x:

Parameter y:

Egg‑shaped clothoid spiral

By editing the Start / End radius for an Entry / Exit transition from Infinite to a required radius it is possible to define an egg shaped clothoid. To return to an infinite radius, select Infinite from the pop‑up menu.

Cubic spiral

The cubic spiral is defined by the length of the spiral and the radius of the adjoining arc. The formulae for the x and y parameters in terms of these two values are as follows:

Parameter x:

Parameter y:

Bloss spiral

Parameter x:

Parameter y:

The Bloss spiral can only be fully developed, that is, for an entry transition the start radius is infinite and similarly for an exit transition the end radius is infinite.

Korean cubic parabola

This cubic parabola is defined by the length of the parabola and the radius of the adjoining arc. The formulae for the x and y parameters in terms of these two values are as follows:

Parameter x:

Parameter y:

The Korean cubic parabola can only be fully developed, that is, for an entry transition the start radius is infinite and similarly for an exit transition the end radius is infinite.

NSW cubic parabola

The NSW cubic parabola is a special parabola used for rail projects in New South Wales, Australia. It is defined by the length of the parabola and an m value. Refer to NSW Government Technical Note ESC 210 Track Geometry and Stability.