Curves used on highways – which type is generally provided? Among the following, which curve type is generally provided on highways to ensure a gradual change of curvature and comfortable steering?

Introduction / Context:
Curves are essential to connect tangents in highway alignments. For safety and comfort, a gradual change in curvature and superelevation is needed as vehicles move from a straight to a circular arc.

Given Data / Assumptions:

• Standard two-lane highway geometry.
• Need to limit lateral jerk and provide progressive superelevation runoff.

Concept / Approach:
A transition curve (e.g., clothoid/spiral) provides a curvature that increases linearly with length, enabling a smooth shift from zero curvature on the tangent to the constant curvature on the circular arc. This improves driver comfort, reduces skidding risk, and eases construction of superelevation.

Step-by-Step Solution:

Verification / Alternative check:
Design manuals require transition curves on most modern highways above certain speeds/deflection angles; purely circular connections are now rare except at very low speeds.

Why Other Options Are Wrong:
Critical curve is not a standard highway term in this context. Vertical curves address grade changes, not horizontal curvature transitions. All the above cannot be right as the first item is incorrect. Reverse without transition is discouraged due to abrupt curvature change.

Common Pitfalls:
Omitting transitions at higher speeds; too-short transitions causing abrupt steering and superelevation runoff.

Final Answer:
Transition curve