Valley Curves or Sag Curves

Valley curves, also known as sag curves, are a type of horizontal curve used in transportation engineering to transition between a descending gradient and an ascending gradient. These curves are designed to provide a smooth and safe transition for vehicles traveling along a roadway.

Maximum Possible Deviation Angle

The maximum possible deviation angle refers to the largest angle that can occur between the tangent lines at the beginning and end of a valley curve. This angle is important because it affects the overall design of the curve and the safety of vehicles navigating through it.

Descending Gradient Meets with an Ascending Gradient

The correct answer to the question is option 'A', which states that the maximum possible deviation angle is obtained when a descending gradient meets with an ascending gradient. This means that when a roadway is sloping downward and transitions to an upward slope, the maximum angle of deviation can occur.

Explanation

When a descending gradient meets with an ascending gradient, the road profile changes from a downward slope to an upward slope. This transition can create a sharp change in the alignment of the roadway, leading to a higher maximum deviation angle.

The maximum deviation angle occurs at the point where the road is at its steepest slope. At this point, the road alignment changes abruptly, which can potentially cause discomfort or even loss of control for drivers if not properly designed.

By designing a valley curve, engineers can smoothen this transition and reduce the maximum deviation angle. The curve allows the roadway to gradually change alignment, providing a more comfortable and safer driving experience.

In contrast, when ascending gradients meet with each other, the change in alignment is not as abrupt. The roadway is already sloping upwards, and the transition between gradients is smoother. Therefore, the maximum deviation angle is typically lower in this scenario.

Conclusion

In conclusion, the maximum possible deviation angle is obtained when a descending gradient meets with an ascending gradient. This is because the change in alignment is more abrupt in this scenario, requiring the use of valley curves to provide a smooth and safe transition for vehicles. By understanding and designing for this maximum angle, engineers can ensure the safety and comfort of drivers on the roadway.