Types of highway horizontal curves – identify the incorrect option On highways, which of the following listed as a “circular curve” type is incorrect?

Introduction / Context:
Horizontal curve classification is fundamental to geometric design. Simple, compound, and reverse curves are standard horizontal curve types. Vertical curves, however, belong to longitudinal profile design and are not circular in standard practice.

Given Data / Assumptions:

• We are classifying curve types used in highway alignment.
• “Circular curves” here refers to horizontal alignment elements using constant radius segments.

Concept / Approach:
Simple, compound, and reverse curves are all built from constant-radius arcs in plan. Vertical curves are used in profile to connect grades; they are typically parabolic to provide a uniform rate of change of grade, not circular.

Step-by-Step Solution:
Identify horizontal circular curve types: simple, compound, reverse → correct.Identify vertical curve: used in profile with parabolic form → not a circular curve type.Therefore, the incorrect option is vertical curves.

Verification / Alternative check:
Sight distance and comfort analyses for vertical curves rely on parabolic geometry; this further confirms they are not circular.

Why Other Options Are Wrong:
Options (a), (b), and (c) are valid classifications of circular curves in plan view.

Common Pitfalls:
Confusing plan and profile elements; assuming all curves are circular regardless of orientation.

Final Answer:
vertical curves