Final answer:
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