Question

For the given highway curve answer questions a. through d. You must show work to receive credit. If you are reading a value from a table state which table and circle the value in the table. (30 points) Given: four-lane (i.e. two lanes in each direction), two-way highway Design Speed =60mph Normal Crown slope is 2% Δ=22 degrees R=2000ft e

max
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=10% P.I. Station =10+00.00 SSD=570ft a) Find the Curve Data for this curve? b) Find the P.C. and P.T. stations. c) Determine the superelevation runoff and runout lengths. d) For the transition from full superelevation to normal crown determine the stations at which the road begins transition from full superelevation, outside-lane crosses zero percent, end inside-lane transition, and return to normal crown.

Answer 1

For a given highway curve, the curve data includes the design speed, normal crown slope, angle of deflection, radius, maximum superelevation, P.I. station, and SSD. The P.C. and P.T. stations can be calculated using the P.I. station and the radius of the curve. The superelevation runoff and runout lengths can be calculated using the radius of the curve and the maximum superelevation. The stations at which the road begins transition from full superelevation, outside-lane crosses zero percent, end inside-lane transition, and returns to normal crown can also be determined.

Step-by-step explanation:

a) Curve Data:
Design Speed = 60mph
Normal Crown slope = 2%
Δ = 22 degrees
R = 2000ft
e max = 10%
P.I. Station = 10+00.00
SSD = 570ft

b) P.C. and P.T. stations:
P.C. station is the Point of Curvature, which is the beginning of the curve. P.C. station = P.I. station - R = 10+00.00 - 2000ft
P.T. station is the Point of Tangency, which is the end of the curve. P.T. station = P.I. station + R = 10+00.00 + 2000ft

c) Superelevation runoff and runout lengths:
Superelevation runoff length is the distance from the P.C. station to the point where the superelevation reaches zero. Superelevation runout length is the distance from the P.T. station to the point where the superelevation returns to normal crown. These lengths can be calculated using the formula:
Runoff/Runout Length = 2πR × e max
where R is the radius of the curve and e max is the maximum superelevation.

d) Transition stations:
The stations at which the road begins transition from full superelevation, outside-lane crosses zero percent, end inside-lane transition, and returns to normal crown can be determined using station equations based on the length of the transition section and the total length of the curve.