Step 1: Understanding the settlement types.
- Circular settlements are typically found in areas with a central point and roads radiating from it, often used in older city designs. This pattern is not common along roads or rivers.
- Linear settlements occur along a transportation route, such as a road, river, or canal. This pattern is common where settlements develop along waterways or roads for trade or access.
- Square and rectangular settlements generally refer to planned, grid-like city layouts, more common in newer urban designs rather than along roads or rivers.
Step 2: Conclusion.
The most common settlement type along roads, rivers, or canals is linear, as settlements are typically built in a line along these features for accessibility and trade.
\[
\boxed{\text{Thus, the correct answer is Linear.}}
\]
Functional classification of urban settlement