Question

Calculate the stopping sight distance on a highway at a descending gradient of 2% for a design speed of 80 kmph, and brake efficiency is 70%. Assume other data as per IRC recommendation.

Answer 1

The stopping sight distance on a highway at a descending gradient of 2% for a design speed of 80 kmph is 287.8 meters.

Step-by-step explanation:

The stopping sight distance on a highway at a descending gradient of 2% for a design speed of 80 kmph can be calculated using the equation:

SSD = (Dv^2 / 2g) + (vT) + (0.278vR)

Where:

• SSD is the stopping sight distance
• Dv is the sum of the maximum distance traveled during perception, reaction, and braking in meters
• g is the grade percentage (2% in this case)
• v is the design speed in meters per second
• T is the perception/reaction time in seconds (1.5 seconds for urban roads)
• R is the braking deceleration rate in meters per second squared (provided by IRC recommendation as 5 m/s² for dry conditions)

Substituting the given values, we have:

SSD = (Dv^2 / 2g) + (vT) + (0.278vR) = (80/2*0.02) + (80*1.5) + (0.278*80*5) = 287.8 meters