If an ascending gradient of 1 in 50 meets a descending gradient of 1 in 50, the length of summit curve for a stopping sight distance of 80 m will be A. zero B. 64m C. 80m D. 60m

The correct answer is B. 64m.

The length of a summit curve is calculated using the following formula:

$L = \frac{S_{sd}}{0.085} \sqrt{\frac{v^2}{g}}$

where:

• $L$ is the length of the summit curve in meters
• $S_{sd}$ is the stopping sight distance in meters
• $v$ is the design speed in kilometers per hour
• $g$ is the acceleration due to gravity in meters per second squared

For a stopping sight distance of 80 m, a design speed of 80 km/h, and an acceleration due to gravity of 9.81 m/s^2, the length of the summit curve is:

$L = \frac{80}{0.085} \sqrt{\frac{80^2}{9.81}} = 64$ m

Option A is incorrect because the length of a summit curve cannot be zero. Option C is incorrect because the stopping sight distance is 80 m, not 80 km. Option D is incorrect because the length of a summit curve is not 60 m.