Examples & Applications: Complex Vertical Curves
Symmetrical Parabolic Vertical Curves
Example 1: Elevation of Highest Point on a Symmetrical Crest Curve
Problem: A symmetrical parabolic vertical curve has a length . The initial grade is and the final grade is . The Point of Vertical Intersection (PVI) is located at station with an elevation of . Calculate the station and elevation of the highest point on the curve.
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Example 2: Determining Point of Vertical Tangency (PVT)
Problem: A symmetrical parabolic vertical curve has a length . The initial grade is and the final grade is . The Point of Vertical Curvature (PVC) is located at station with an elevation of . What is the elevation of the Point of Vertical Tangency (PVT)?
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Example 3: Elevation at Any Point on Symmetrical Curve
Problem: For the same symmetrical vertical curve (Example 2), calculate the vertical offset at a horizontal distance from the PVC.
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Unsymmetrical Parabolic Vertical Curves
Example 4: Calculating External Distance for Unsymmetrical Curve
Problem: An unsymmetrical parabolic vertical curve has a total length . The horizontal distance from the PVC to the PVI is and the distance from the PVI to the PVT is . The initial grade is and the final grade is . What is the external distance at the PVI?
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Example 5: Designing an Unsymmetrical Curve to Fit Constraints
Problem: A highway passing under a bridge requires an elevation of at least at the PVI station to maintain clearance. The PVC is at elevation and . The initial grade is . What is the maximum length of if the final grade is to ensure the sag curve clears the bridge constraints? The external distance must not raise the curve above at the PVI.
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Example 6: Evaluating PVI Offset
Problem: For an unsymmetrical curve with , , , and , calculate the difference in elevation between the initial tangent at the PVI and the curve itself at that same station.
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Sight Distance on Vertical Curves
Example 7: Determining Curve Length Based on Stopping Sight Distance (Crest, S < L)
Problem: A crest vertical curve must be designed for a stopping sight distance of . The initial grade is and the final grade is . Assuming driver eye height and object height , determine the required length of the curve. Assume .
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Example 8: Verifying Sight Distance (Sag Curve, S < L)
Problem: A sag vertical curve has a length . The grades are and . The stopping sight distance required is . Determine if the curve provides adequate headlight sight distance. Use the standard formula for sag curves assuming .
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Example 9: Determining Curve Length Based on Stopping Sight Distance (Crest, S > L)
Problem: A minor crest vertical curve connects an initial grade of and a final grade of . The required stopping sight distance is . Assuming driver eye height and object height , determine the required length of the curve. Assume .
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