Question

_____________ curves are curves which, when viewed from the side, are concave upwards. This includes vertical curves at valley bottoms, but it also includes locations where an uphill grade becomes steeper, or a downhill grade becomes less steep.

(a) Sag horizontal

(b) Hog horizontal

(c) Sag vertical

(d) Hog vertical

This question was addressed to me in a job interview.

My question is from Estimate of Metalled Roads topic in division Road Estimating, Sanitary and Water Supply Work of Civil Engineering Drawing

Answer 1

Right answer is (c) Sag vertical

Explanation: The most important design criterion for these curves is headlight sight distance. When a driver is driving on a sag curve at night, the sight distance is limited by the higher grade in front of the vehicle. This distance must be long enough that the driver can see any obstruction on the road and stop the vehicle within the headlight sight distance. The headlight sight distance (S) is determined by the angle of the headlight and angle of the tangent slope at the end of the curve.