A priority intersection has a single-lane one-way traffic road crossing an undivided two- lane two-way traffic road

Q. A priority intersection has a single-lane one-way traffic road crossing an undivided two- lane two-way traffic road. The traffic stream speed on the single-lane road is 20 kmph and the speed on the two-lane road is 50 kmph. The perception-reaction time is 2.5 s, coefficient of longitudinal friction is 0.38 and acceleration due to gravity is 9.81 m/s². A clear sight triangle has to be ensured at this intersection. The minimum lengths of the sides of the sight triangle along the two-lane road and the single-lane road, respectively will be

(A) 50 m and 20 m                                             (B) 61 m and 18 m

(C) 111 m and 15 m                                           (D) 122 m and 36 m

Ans: 111 m and 15 m 

Sol:

As per data given and based on calculation of SSD the answer would be 61 m and 18 m. But, as per the code IRC:66 of sight distance calculation at priority intersection should be formed by measuring a distance of 15 m along minor roads and a distance equal to 8 seconds travel at the design speed.
(50×0.278×8=111m) along the major road. Hence, answer will be 111 m and 15 m.