A vertical curve is needed to join to tangents; G₁=5% and G2=2%. Assuming the worst case scenario for braking, and the AASHTO recommended values for deceleration and perception-reaction time, calculate the minimum length of curve (ft) needed to satisfy the safety criteria. The design speed is 50 mph. Response Feedback: G₂-G₁ is negative, therefore a crest curve. A=3 SSD(-G1)=463.6 ft If you assume SL, Lmin=208 ft. SSD is greater than Lmin. The assumption is good.

A vertical curve is needed to join to tangents; G₁=5% and G2=2%. Assuming the worst case scenario for braking, and the AASHTO recommended values for deceleration and perception-reaction time, calculate the minimum length of curve (ft) needed to satisfy the safety criteria. The design speed is 50 mph. Response Feedback: G₂-G₁ is negative, therefore a crest curve. A=3 SSD(-G1)=463.6 ft If you assume SL, Lmin=208 ft. SSD is greater than Lmin. The assumption is good.

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Concept explainers

Curve setting

A curve is a turn that is provided horizontally or vertically in the design of highways, railways, and runways. A curve connects two straight lines that are separated by the deflection angle. It helps to change the direction and alignment of the highways, railway tracks, and runways. Therefore, the gradual change in their alignment is made by using a curve to provide comfort to the passengers and this also provides an easy turn to change the direction of the moving vehicle.

Question

A vertical curve is needed to join to tangents; G₁-5% and G2-2%. Assuming the worst case scenario for
braking, and the AASHTO recommended values for deceleration and perception-reaction time, calculate the
minimum length of curve (ft) needed to satisfy the safety criteria. The design speed is 50 mph.
Response
Feedback:
G2-G₁ is negative, therefore a crest curve.
A=3
SSD(-G1)=463.6 ft
If you assume S<L, Lmin=299 ft. SSD is not less than Lmin. The assumption does not
hold.
If you assume S>L, Lmin=208 ft. SSD is greater than Lmin. The assumption is good.

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