Intersection safety – crossing conflicts: At a road junction, crossing conflicts (the most severe type of conflict) primarily occur under which condition for the intersecting approaches?

Introduction / Context:
Safety at intersections depends on the number and type of vehicle conflict points—crossing, merging, and diverging. Crossing conflicts are the most severe because they involve near-perpendicular trajectories with high crash energy. Recognizing when these conflicts exist helps engineers choose appropriate control, channelization, and geometric design measures.

Given Data / Assumptions:

• A generic at-grade intersection (no grade separation).
• Approaches may be one-way or two-way.
• We are focusing on crossing conflicts specifically.

Concept / Approach:
Two-way roads on both approaches allow movements from both directions on each road, creating the maximum set of potential conflict points. One-way approaches reduce or eliminate direct crossing movements because opposing directions are segregated, leaving mostly merging and diverging conflicts.

Step-by-Step Solution:
Identify movement sets for each intersection type.For two two-way roads, through and turning movements from opposing directions intersect, creating many crossing points.For any case involving one-way roads, opposing flows are reduced and thus crossing conflicts diminish.

Verification / Alternative check:
Standard diagrams show around 32 total conflicts for a full four-leg two-way intersection, with 16 of them crossing. Converting one or both approaches to one-way reduces crossing conflicts significantly, confirming the selection.

Why Other Options Are Wrong:

• Both one-way roads: crossing conflicts are minimized or eliminated.
• One way + two way: fewer crossing conflicts than the two-way plus two-way case.
• None of these: incorrect because crossing conflicts clearly occur for two-way on both approaches.

Common Pitfalls:

• Confusing crossing conflicts with merging/diverging conflicts, which are less severe.
• Ignoring turn prohibitions and channelization that can alter conflict counts.

Final Answer:
both are two-way roads