Standard rail lengths worldwide 30 m-long rails are (historically) used predominantly in which country's railway practice?

Introduction / Context:
Rail lengths have varied by country due to manufacturing capabilities, handling limits, and legacy standards. Recognizing typical lengths helps avoid confusion when solving track design and maintenance problems that reference foreign practices.

Given Data / Assumptions:

• The question targets the 30 m standard length and asks which country historically used it.
• We consider legacy jointed-track practice rather than modern long-welded rail (LWR/CWR).

Concept / Approach:
Historically, the U.K. adopted approximately 30 m rail lengths in certain eras as an efficiency compromise between joint reduction and handling practicality. By contrast, India traditionally used 13 m and later 26 m; U.S.A. commonly referenced 39 ft; Russia and Pakistan also had different standards.

Step-by-Step Solution:
Match 30 m to known legacy standards internationally.Associate 30 m with British practice historically cited in exam literature.Select U.K. as the correct option.

Verification / Alternative check:
Permanent-way comparative tables and exam guides list 30 m for the U.K., aligning with this answer.

Why Other Options Are Wrong:

• India/Pakistan: typically 11.89–13 m and 26 m (later), not 30 m.
• U.S.A.: 39 ft (≈11.89 m) common historically.
• Russia: often 25 m or other standards.

Common Pitfalls:
Confusing modern CWR practice with historic jointed lengths; mixing India’s 26 m rails with the 30 m figure.

Final Answer:
U.K.