< b="" />Explanation: < />

The extra width of pavement is provided on a horizontal curve. Here is a detailed explanation of why this is the correct answer:

< b="" />Horizontal Curve: < />
A horizontal curve is a section of a road where the alignment changes from a straight line to a curve. It is designed to allow vehicles to smoothly transition from one direction to another. Horizontal curves are necessary for roads that follow the natural terrain or when there are obstacles that need to be avoided.

< b="" />Need for Extra Width: < />
When a vehicle travels on a horizontal curve, it experiences centrifugal force which tends to push it outwards. This outward force increases with the speed of the vehicle and the sharpness of the curve. To counteract this force and ensure the safety of the vehicle, extra width is provided on the pavement.

< b="" />Safety Considerations: < />
The extra width of pavement on a horizontal curve serves several safety purposes:

< b="" />1. Vehicle Stability: < />
By providing extra width, the pavement allows vehicles to maintain stability while negotiating the curve. It provides additional space for the tires to grip the road and prevents the vehicle from sliding or skidding.

< b="" />2. Overrun Area: < />
The extra width acts as an overrun area, providing a buffer zone in case a vehicle loses control or overshoots the curve. This space allows the driver to bring the vehicle back under control without colliding with any obstacles.

< b="" />3. Clearance for Larger Vehicles: < />
The additional width also accommodates larger vehicles, such as trucks or buses, which require more space to maneuver on curves. Providing sufficient clearance prevents these vehicles from encroaching onto the adjacent lane or shoulder.

< b="" />4. Driver Comfort: < />
The wider pavement on a horizontal curve improves driver comfort by reducing the perception of a sudden change in direction. It allows for smoother and more gradual turning movements, minimizing the discomfort or unease experienced by the driver and passengers.

< b="" />Conclusion: < />
In conclusion, the extra width of pavement is provided on a horizontal curve to ensure the safety and stability of vehicles while negotiating the curve. It provides a buffer zone, accommodates larger vehicles, and enhances driver comfort.