Pot sleepers (two-bowl type): The total effective bearing area of both bowls of a pot sleeper, when compared with a wooden sleeper, is

Introduction / Context:
Pot sleepers (cast-iron, two-bowl type) were historically used on Indian Railways. Their design intent was to provide bearing performance comparable to timber sleepers by distributing load over an equivalent bearing area.

Given Data / Assumptions:

• Two bowls support the rail through chairs or keys.
• Comparison is with a standard wooden sleeper under similar loading.

Concept / Approach:
The total effective bearing area (sum of both bowls in contact with ballast) is chosen to match the contact area of a timber sleeper so that ballast pressure levels are similar, avoiding overstressing of formation and ensuring comparable settlement behaviour.

Step-by-Step Solution:
Recognize that bearing area determines average ballast pressure p = Load / Area.Design intent keeps p similar between sleeper types to maintain track stability.Hence the two bowls together provide an area approximately equal to that of a timber sleeper.

Verification / Alternative check:
Historic specifications targeted equality of bearing pressure, which implies near-equal effective bearing areas for comparable axle loads.

Why Other Options Are Wrong:

• Slightly more/less: Would lead to different ballast pressures and performance; not the intent for interchangeable usage.
• None of these: Incorrect because equivalence was the design goal.

Common Pitfalls:
Comparing plan area rather than effective bearing area actually contacting ballast; ignoring fouling or consolidation which changes effective support.

Final Answer:
equal to that of a wooden sleeper