Longitudinal gradient interpretation: Three points A, B, and C, 500 m apart on a straight road, have reduced levels 500 m, 505 m, and 510 m respectively. What does this indicate about the gradient between A and C?

Introduction / Context:
Reduced levels (RLs) are elevations above a datum. Longitudinal profiles use RLs to determine up- or down-grades. Understanding the sign and magnitude of gradient is crucial for drainage, fuel economy, and safety.

Given Data / Assumptions:

• A, B, C are collinear along the road at equal spacing of 500 m.
• RL(A) = 500 m, RL(B) = 505 m, RL(C) = 510 m.
• Chainage increases from A → B → C.

Concept / Approach:

If the RL increases with chainage, the road climbs: that is a positive gradient. Here, elevation increases by 5 m every 500 m, indicating a uniform ascending grade between A and C.

Step-by-Step Solution:

Verification / Alternative check:

Graphing RL versus chainage shows a straight rising line; no change in sign occurs between segments.

Why Other Options Are Wrong:

• No gradient: false; RL clearly changes.
• Negative gradient: RL decreases with chainage would be required; opposite is observed.
• Mixed gradients: both segments are uniformly rising, not mixed.

Common Pitfalls:

• Confusing positive/negative gradient sign conventions with slope direction on plots.

Final Answer:

A positive gradient between A and C.