What does the term "horizontal alignment" in roadway design refer to?

The term "horizontal alignment" in roadway design pertains specifically to the path of the roadway as it exists on a flat horizontal plane. This involves the directional changes of the road, including straight segments and curves that define how the roadway aligns itself across the landscape. Proper horizontal alignment is crucial for ensuring safe and smooth vehicle movement, as it considers factors like the radius of curves and sight distances to enhance both operational efficiency and safety.

Understanding horizontal alignment is essential for engineers and planners because it affects vehicle dynamics, driver perception, and overall traffic flow. Adequate horizontal alignment can minimize sharp turns that could lead to accidents and provide a more comfortable driving experience. In contrast, other options such as vertical curvature, elevation adjustments, and material choices pertain to different aspects of roadway design which do not specifically define the horizontal path of the roadway.