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A Process for Road Layout

Road Design

• Check the existing Topographical data

Road Design

• Decide on the type of road and characteristics – Freeway– Arterial– Collector– Feeder

Road Design

Setting up a chart for survey data and control points

Road Design

Transit Line

Setting up the 90° Intersection

Road Design

• Plan the Start of the Curve (PC)

Road Design

Add information to the chart

Road Design

Layout the Curve

Road Design

Now Calculate the Unknowns about the curve.

Curve information

Knowns

R=300’

∆=33°34’

Road Design

180R

L

To find the distance from P.C. to P.T. use the formula

Road Design

180

'3433'300L

Road Design

Convert 33°34’ to degrees

34’/60’=.567 33°34’ =33.567°

Road Design

Road Design

Back to the Formula

180

567.33'300L

L=175.756’

Road Design

Finding the angle of the 100’ chord (D)

Bisect the angle to create a Right Triangle

Xsin30050

Inverse SinX=9.594°

D=2(9.594°)

D=19.1881°

D=19°11’

Road Design

Add information to the chart

Continue laying out the road and points

Road Design

Road Design

To create the vertical profile of the road, lines are dropped from the station points and an exaggerated vertical scale is created. Elevation data from existing station points are plotted to a graph.

A line is plotted through the points. The line is then smoothed and parabolic transitions are added between slopes.

Road Design

Road Design

Vertical information is transferred back to the

control points.