GATE 2019 CE (CE1) – Question 57
A parabolic vertical curve joins grades +5% and −3%. Horizontal curve length is 400 m. VPC lies on the +5% grade. Find the height difference between the vertical point of curvature VPC and vertical point of intersection VPI (m), to the nearest integer.
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Correct answer: 10 to 10 OR -10 to -10
Explanation
VPI lies halfway along the 400 m horizontal curve length, 200 m from VPC on the initial tangent. Its height above VPC is $0.05(200)=$ **10 m**. The official key accepts both +10 and −10 because subtraction order changes the sign. This is tangent-intersection elevation, not the curve’s midpoint elevation.