Correct Answer - Option 4 : 20 kmph
Explanation:
According to IRC, ruling minimum and absolute minimum value of radii of the horizontal curve on the basis of design speed:
emax = 7 % (for Plain and rolling), 4 % ( urban) and 10 % (Hilly) and f = 0.15
Suggested design speeds (kmph) in India:
|
Classification of roads
|
Plain Terrain
|
Rolling Terrain
|
|
| |
| |
Ruling
|
Absolute
|
Ruling
|
Absolute
|
|
|
NH &SH
|
100
|
80
|
80
|
65
|
|
|
MDR
|
80
|
65
|
65
|
50
|
|
|
ODR
|
65
|
50
|
50
|
40
|
|
|
VR
|
50
|
40
|
40
|
35
|
|
From the Table, It is evident that for NH & SH Ruling Speed is 100 kmph & Absolute speed is 80 kmph
∴ Ruling speed is increased by 20 kmph.
The ruling minimum radius is a limiting value of curvature for a given design speed.
A ruling minimum radius (Rruling) is calculated on the basis of maximum superelevation and coefficient of friction. The radius of the curve should be higher than Rruling.
\({R_{ruling}} = \frac{{{v^2}}}{{g(e + f)}}\)
where,
v = velocity (m / s)
g = acceleration due to gravity (m / s2)
e = superelevation
f = lateral coefficient of friction
