Highway drainage – typical side drain width in hilly regions What is the usual (typical) width provided for roadside side drains along highways in hilly terrain?

Introduction / Context:
Roadside side drains collect surface runoff and protect the pavement structure, especially critical on hill roads where rainfall concentration and slopes are high. Proper sizing balances hydraulic capacity, safety, and right-of-way constraints.

Given Data / Assumptions:

• Two-lane hill highway typical section.
• Conventional trapezoidal or rectangular drain.
• Moderate rainfall design with typical maintenance access.

Concept / Approach:
Standard practice provides about 0.6 m (60 cm) width drains in many hill sections, with depth and side slopes chosen for capacity and stability. Wider drains are used for higher discharges, but 60 cm is a common baseline in typical designs.

Step-by-Step Solution:

Verification / Alternative check:
State hill road manuals and many PWD standard drawings frequently show 0.6 m drains for typical stretches, confirming the typical dimension.

Why Other Options Are Wrong:
50 cm can be insufficient for debris-laden flows; 70–100 cm may be specified for heavy runoff but are not the usual minimum.

Common Pitfalls:
Ignoring maintenance needs; not providing check drains and catch pits; inadequate lining leading to scour.

Final Answer:
60 cm