11
Design Elements
General Guide to RoadPlus - 4.0.0en
R
1
R
1
>R
2
parameter A
station E
1
, N
1
station E
2
, N
2
R
2
station E
1
, N
1
station E
2
, N
2
R
2
R
1
R
1
<R
2
parameter A
A
2
= R x L
Curve in
- spiral transition from larger to smaller radius curve.
Curve out
- spiral transition from smaller to larger radius
curve.
Curve in and out
are used for combinations such as:
curve - curve in - curve out - curve
or
tangent - spiral in - curve in - curve
whereas spiral in/out always connect a tangent with a curve /
curve in / curve out.
Parameter A
R
radius of the connecting circular curve
L
length of the spiral in/out or curve in/out
Sign convention for curves and spirals
:
centre of curvature to left of centre line: R resp. A < 0
centre of curvature to right of centre line: R resp. A > 0
Or in words: Looking in the direction of increasing station,
apply the "right hand positive rule".