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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The tangent previous to the curve is called.
A) Back tangent
B) Forward tangent
C) Length of curve
D) Long chord
Back tangent
The tangent line to the curve prior to the point of curve (PC) is known as the back tangent or rear tangent. It represents the original direction of the alignment before entering the curve. The tangent following the curve is referred to as the forward tangent.
The tangent line to the curve prior to the point of curve (PC) is known as the back tangent or rear tangent. It represents the original direction of the alignment before entering the curve. The tangent following the curve is referred to as the forward tangent.
T=Rtan(2Δ) — Tangent length where R is radius and Δ is deflection angle
L=2Rsin(2Δ) — Length of long chord
In highway and railway alignment design, two straight sections (tangents) intersecting at an angle are connected using a circular or transition curve. The line along which the survey proceeds before entering the curve is the back tangent, establishing the initial direction from which deflection angles are measured.
The point where the back tangent touches the curve is called the Point of Curve (PC) or Tangent Point (T₁).
The point where the curve ends and joins the forward tangent is called the Point of Tangency (PT) or Tangent Point (T₂).
The intersection point of the back tangent and forward tangent is called the Point of Intersection (PI) or Vertex (V).
Used in setting out horizontal curves for roads and railways.
Essential for calculating tangent lengths and curve elements during route surveys.
Option B (Forward tangent) is the tangent line immediately following the curve along the direction of alignment.
Option C (Length of curve) is the arc length from the Point of Curve (PC) to the Point of Tangency (PT).
Option D (Long chord) is the straight distance joining the Point of Curve (PC) to the Point of Tangency (PT).
A is correct — The back tangent is the straight section preceding the curve in the direction of the survey.
Remember that alignment stationing proceeds along the back tangent to the PC, along the curve to the PT, and then continues along the forward tangent.