Gaps exist in railway tracks and sidewalks to allow for thermal expansion and contraction due to temperature changes.

1. Railway Tracks

• Material: Steel (used for rails) expands when heated and contracts when cooled.
• Reason for Gaps: Without gaps, the expansion could cause the rails to buckle or warp, leading to dangerous conditions such as derailments.
• Expansion Joints: In some modern tracks, especially continuous welded rails, expansion joints or anchoring systems are used to manage this thermal expansion safely.

2. Sidewalks

• Material: Concrete expands and contracts with temperature fluctuations.
• Reason for Gaps: The gaps, known as control joints or expansion joints, prevent the concrete from cracking unpredictably due to thermal stress or ground movement.
• These joints allow the sidewalk slabs to move slightly without damaging the structure.

Summary:

Gaps are intentionally included to absorb the stress from expansion and contraction, maintaining safety and structural integrity over time.