Chapter 6 Basic Geometric Constructions 203
Figure 6-54. Connecting two parallel lines with reversing arcs of equal radii. A civil engineer may use this
construction when drawing a highway “S” curve.
A B
B
C D
A B
C
E
D
C
A
B
C
E
F
D
G
D A
Connect Two
Parallel
Lines with Reversing Arcs
of Equal Radii
CAD
Using a Compass
(Manual Procedure)
1. Lines AB and CD are given, Figure 6-54A.
2. Draw a line between Points B and C.
Divide Line BC into two equal parts
(Lines BE and EC), Figure 6-54B.
3. Construct perpendicular bisectors of
Lines BE and EC, Figure 6-54C.
4. Draw perpendiculars to Lines AB and
CD at Points B and C.
5. The points of intersection of the bisec-
tors and perpendiculars at Points F and
G are the centers for drawing the equal
arcs (Arcs FB and GC). These arcs are
tangent to each other and to the parallel
lines.
An application of this construction in a
highway drawing is shown in Figure 6-54D.
Using the Center, Start, End
Option and Continue Option
(CAD Procedure)
1. Lines AB and CD are given, Figure 6-55A.
2. Enter the
Line
command and draw a line
between Points B and C. Enter the
Divide
command and divide Line BC into four
equal parts, Figure 6-55B.