This is the first of three AutoCAD exercises where we will develop a preliminary design (i.e. plan,
profile, and cross section) for a new road connecting from Southwest Road to North Road as shown on
the attached map.
Alternate B is a 2-lane highway with 11-foot lanes and 6-foot shoulders.
Preliminary estimates indicate that 120-feet of right-of-way is needed for the project.
In this exercise,
we will develop a horizontal alignment for alternate B.
A field survey and preliminary design work provided the following information:
Beginning station: 10+00
Curve #1 data
PI:
39+75.72
Deflection angle: 87.42° (Curve to the left)
Radius:
1315’
Curve #2 data
PI:
74+95.85
Deflection angle: 50.1249° (Curve to the right)
Radius:
980’
Ending station: 84+10.14 (surveying) or 78+43.15 (along centerline) depending on how stations are
measured (along alignment or along tangents).
The submitted AutoCAD drawing should
clearly show the centerline, edges of pavement, and limits
of right of way
.
Label
all relevant
information: stationing, PC, PT, PI, BS, ES, curve data (i.e. R, L, and delta), x1, x2,
x3, and bearings with appropriate measurements and units.
Be sure to include a scale and north arrow.
Plot the drawing on 11”x17” paper.
Hand Calculations:
BS, PI, PC, PT, T, L (for both curves) and ES (all calculations should be based on
measurements along the centerline).
Equations for Assignment #1
Relevant Curve Equations
T = R tan (Δ/2)
L = R * Δ, where Δ is in radians
Station Equations
PC
A
= PI
A
- T
A
PT
A
= PC
A
+ L
A
For subsequent curves:
PI
B
= PT
A
+ x
2
- T
A
PC
B
= PI
B
- T
B
PT
B
= PC
B
+ L
B
2