Preventing rail creep with steel sleepers To minimize rail creep on steel-sleepered track, rails are secured using clips, bolts, and how many keys?

Introduction / Context:
Rail creep (longitudinal movement of rails) leads to joint gaps and geometry defects. On steel sleepers, particular fastening arrangements help resist this movement by providing adequate longitudinal restraint.

Given Data / Assumptions:

• Steel sleepers are assumed to use clips, bolts, and keys.
• We are focusing on the typical number of keys employed to prevent creep effectively.

Concept / Approach:
Traditional steel-sleeper arrangements often employ double-keyed systems—two keys—providing opposed bearing to reduce longitudinal slip. This symmetric restraint enhances holding power compared with single-key arrangements.

Step-by-Step Solution:
Recognize that creep prevention relies on friction and mechanical interlock.Double-key (two keys) systems brace the rail foot on both sides.Hence, select 'Two keys' as the standard answer used in many exam references.

Verification / Alternative check:
Old permanent-way manuals and question banks commonly specify two keys for steel sleeper anti-creep arrangements.

Why Other Options Are Wrong:
One key offers less restraint; three or four keys are not standard practice for typical steel-sleeper fastenings and would be impractical.

Common Pitfalls:
Assuming heavier clips alone are sufficient; proper keying pattern is critical to creep control.

Final Answer:
Two keys