Maximum polar angle for a right-angle bend with full transitions For a 90° road bend provided with transition curves throughout, the maximum polar angle used in setting out is typically:

Introduction / Context:
When setting out curves with transitions, the polar deflection (setting-out) method uses a limiting polar angle for accurate pegging of points along the transition and circular arc. For a right-angle (90°) deflection, a conventional maximum polar angle is adopted to maintain layout accuracy.

Given Data / Assumptions:

• Total central deflection is 90°.
• Transition is provided throughout (entry and exit).
• Standard field methods limit per-setup angular increments for precision.

Concept / Approach:
Using a smaller maximum polar angle reduces setting-out errors and provides a sufficient number of points for a smooth curve. A commonly used value in practical fieldwork for such bends is about 15°, striking a balance between effort and accuracy.

Step-by-Step Solution:

Verification / Alternative check:
Field manuals frequently suggest 10–15° increments; for a 90° bend, 15° yields six segments, adequate for peg density without excessive workload.

Why Other Options Are Wrong:
10° is acceptable but increases work; 20–45° provide too coarse control and may degrade smoothness.

Common Pitfalls:
Using overly large polar angles on sharp bends; mixing polar angle with deflection angle from tangent.

Final Answer:
15°