Identification of flexible pavement types: Which of the following road types are generally classified as flexible pavements?

Introduction / Context:
Pavements are commonly categorized as flexible or rigid based on how they distribute wheel loads. Flexible systems rely on layered granular/bituminous materials and exhibit comparatively small flexural stiffness, allowing gradual load dispersion to the subgrade.

Given Data / Assumptions:

• Typical highway construction practices are considered.
• WBM, stabilized soil, and bituminous layers are familiar flexible components.

Concept / Approach:
Flexible pavements include constructions like WBM, stabilized soil bases/sub-bases, and multi-layer bituminous surfacings. All of these fall under the flexible category because the structure acts through layered load distribution rather than slab action as in rigid (concrete) pavements.

Step-by-Step Solution:
Identify typical flexible components (WBM, stabilized soil, bituminous layers).Confirm that each listed option belongs to flexible pavement practices.Choose the comprehensive answer including all listed types.

Verification / Alternative check:
Design methods such as CBR or mechanistic-empirical flexible pavement design explicitly consider granular/bituminous layers—consistent with all options a–c.

Why Other Options Are Wrong:

• Individual options a–c are correct but incomplete standing alone.
• None of these: incorrect because all are flexible.

Common Pitfalls:

• Confusing “lean concrete base” (semi-rigid/composite) with fully flexible systems.
• Ignoring drainage and moisture sensitivity of flexible layers which strongly affect performance.

Final Answer:
All the above