The steepest gradient permissible on a 2.5° curve for B.G. line having ruling gradient of 1 in 200 is:

Concept:

Grade compensation (GC):

(i) If there is any curvature along with the gradient then some compensation has to be made in terms of two types of resistance.

(ii) One is resistance offered by the gradient and the other is resistance offered by the curvature.

BG → 0.04% per degree of curve

MG → 0.03% per degree of curve

NG → 0.02% per degree of curve

Permissible gradient = Ruling gradient – Gradient compensation

Calculation:

Given, Degree of curve = 2.5° 

Ruling gradient 1 in 200

\(= \frac{1}{{200}} \times 100\% = 0.5\%\)

Permissible gradient = Ruling gradient – Gradient compensation

= 0.5% - 0.04% × D°

= 0.5% - 0.04 × 2.5

= 0.4 %  

\(= \frac{{0.4}}{{100}} = \frac{1}{{250}}\)