Correct Answer - Option 3 : Both (A) and (B)
Concept:
Length of transition curve (Maximum value is to be considered among the below options)
a) Based on the rate of change of centrifugal acceleration (c)
\({{\rm{l}}_{\rm{s}}} = \frac{{{v^3}}}{{c \times R}}\)
where \(c = \frac{{80}}{{75 + V}}\) ……….. c value should be between 0.5 to 0.8
b) Based on the rate of change of superelevation (e)
1. Superelevation attained by rotation about the inner edge or outer edge
\({l_s} = eN\left( {w + w \times e} \right)\)
2. Superelevation attained by rotation about the center
\({l_s} = \frac{{eN\left( {w + w \times e} \right)}}{2}\)
c) Based on IRC Formula
\({l_s} = \frac{{{V^2}}}{R}\) for Hilly terrain and \({l_s} = \frac{{2.7{V^2}}}{R}\) for Plain and Rolling terrain.
Where
Ls = length of the transition curve (m), v = speed of the vehicle (m/s), V = speed of the vehicle (km/hour),
e = required superelevation, N = rate of change of superelevation to be attained, R = radius of the transition (m), and
w = width of road/pavement
∴ The length of a transition curve depends on the rate of change of centrifugal acceleration and rate of change of super elevation.
