Vertical alignment of a highway refers to the design of the road in terms of its vertical profile, including the grades or slopes, curves, and other features that affect the vertical movement of vehicles along the roadway. It is an important aspect of highway design to ensure safe and efficient transportation.

Grades:
- One of the key elements of vertical alignment is the determination of grades or slopes along the highway. This involves deciding the rate at which the road rises or falls over a given distance. It is important to design grades that are within acceptable limits to provide a smooth and comfortable driving experience while also considering the safety of the drivers.
- The grades should be designed in such a way that they do not exceed the capabilities of vehicles, particularly heavy trucks, to climb or descend without excessive speed or loss of control. This requires considering factors such as vehicle performance, road geometry, and the terrain.

Curves:
- The design of valley curves is another aspect of vertical alignment. Valley curves are used to connect two different vertical grades, such as a downhill section to an uphill section, while maintaining a smooth transition for vehicles.
- The vertical alignment of a highway should ensure that the curves are designed to provide adequate sight distance for drivers, allowing them to see and react to potential hazards on the road ahead. This involves considering factors such as the design speed of the road, the curvature of the curve, and the height of the driver's eye above the road surface.

Other Considerations:
- In addition to grades and curves, other factors related to vertical alignment include the design of ramps and interchanges, which must be carefully designed to provide smooth transitions between different levels of the highway system.
- The vertical alignment also plays a role in the design of drainage systems, as the slopes of the road must be designed to allow for proper runoff of water during rainfall events.
- Highway lighting is not directly related to the vertical alignment of the road, as it is primarily concerned with providing adequate illumination for drivers during nighttime conditions. However, it is an important aspect of overall highway design to ensure safety and visibility.

In conclusion, the vertical alignment of a highway involves the design of grades, curves, and other features to ensure safe and efficient transportation. It includes considerations such as sight distance, design of valley curves, and gradients, while also encompassing other aspects of highway design such as ramps, drainage, and lighting.