Length Of Transition Curve
In this article, I will show you how to design the length of the transition curve, or say how to calculate or determine the length of the transition curve.
The length of the transition curve is designed to fulfil the three condition as mention below. The length of the transition curve for design should be the highest of the three values.
1. The Rate of Change of Centrifugal Acceleration
The rate of change of centrifugal acceleration to be developed gradually. From this consideration the length transition curve is given by the following equation:
Ls = 0.0215 V³/ CR
Where, Ls = Length of transition curve in m, V = Speed of vehicle in Km/h, C = Rate of change of centrifugal acceleration, R = Radius of the circular curve in m.
The minimum and maximum values of C are limited to 0.5 & 0.8 respectively.
2. The Rate of Introduction of Designed Super Elevation
The rate of introduction of designed superelevation to be at a reasonable rate. From this consideration the length of the transition curve is given by the following :
Ls = e.N (W + We)/2
Where, e = The rate of designed superelevation, W = Normal pavement width in m, We = Extra widening pavement at the circular curve in m. 1/N = Rate of change of superelevation (Minimum value of N is 150 to 60 ).
3. By Empirical Formula
According to I.R.C standards, the length of the horizontal transition curve should act, then the value given by the following equations:
a)For plain and rolling terrain
Ls = 2.7 V²/R
b)For mountainous and steep terrain
Ls = V²/R