What does the term "tangent" refer to in the context of circular curves?

In the context of circular curves, the term "tangent" refers to a straight line that touches the curve at a single point without crossing it. This is a fundamental concept in surveying and geometry, particularly in the design of roads and railways. The tangent line serves as an essential reference in horizontal alignment, helping to define the direction of the curve and transition to straight paths.

Understanding the tangent is crucial for engineers and surveyors as it helps in designing smooth transitions between straight sections and curves, ensuring vehicle safety and comfort. The properties of the tangent line, such as its angle with respect to the horizontal or vertical alignment, are also important for calculating sight distances and assessing visibility at intersections and curves.