In highway traffic engineering for at-grade roundabouts (rotaries), the weaving length of a roadway is defined as the distance between which two features of the channelized layout?

Introduction / Context:
Weaving length is a fundamental concept in the design and capacity analysis of modern roundabouts and traditional traffic rotaries in highway engineering. It represents the roadway segment over which vehicles entering and exiting the circulatory carriageway cross paths (weave), and it governs safe operation, speed, and throughput under heterogeneous traffic compositions often found in Indian conditions.

Given Data / Assumptions:

• Facility: at-grade rotary/roundabout with channelised approaches.
• Weaving occurs between successive entry and exit points.
• Channelising (splitter) islands guide entering and exiting streams.

Concept / Approach:
By definition used in design manuals, the weaving length is the distance measured along the circulatory roadway between the ends of two adjacent channelising (splitter) islands. This is the section where streams merge, cross, and diverge. Adequate weaving length allows drivers to change lanes and complete manoeuvres at comfortable deceleration/acceleration rates, thereby limiting conflict and maintaining capacity.

Step-by-Step Solution:
Identify where entering traffic merges with circulating traffic: immediately downstream of the entry splitter island. Identify where exiting traffic diverges toward the next exit: immediately upstream of the exit splitter island. Define weaving segment as the portion between these two splitter islands. Select the option describing this exact distance.

Verification / Alternative check:
Capacity relations for weaving sections use parameters such as weaving length (L_w), weaving width, proportion of weaving traffic, and entry widths. Shorter L_w increases lane-change conflicts and reduces capacity, confirming the necessity of measuring between splitter islands where weaving actually happens.

Why Other Options Are Wrong:

• Half circumference/diameter: Geometric descriptors of the central island, not the conflict segment.
• Total width of adjoining radial roads: A cross-sectional dimension, not a longitudinal distance along the circulatory carriageway.
• Inscribed circle to outer kerb: Radial/offset measure, unrelated to weaving definition.

Common Pitfalls:

• Measuring along the central island edge instead of along the vehicle path between splitter islands.
• Ignoring that weaving begins after the entry nose and ends before the exit nose.

Final Answer:
Between the channelising (splitter) islands.