[amp_mcq option1=”1 in 257″ option2=”1 in 357″ option3=”1 in 457″ option4=”1 in 512″ correct=”option1″]
The correct answer is A. 1 in 257.
The permissible gradient of a horizontal curve of 3° on a gradient of 1 in 250 is calculated using the following formula:
Permissible gradient = 1 + (3/180) * 1 in 250 = 1 + 0.005 = 1.005 in 250 = 1 in 257
The other options are incorrect because they do not take into account the angle of the horizontal curve.