When should staggered formations be avoided?

Staggered formations should be avoided while turning or entering a highway because these maneuvers require more precise positioning and adjustments from each rider. In a staggered formation, riders are positioned one behind the other in adjacent lanes, which provides a certain level of space and visibility. However, when making a turn or merging, the angles and trajectories at which cyclists need to maneuver can create a risk if riders are not in a single-file line. A single-file line ensures that each rider has an unobstructed path and makes it easier to react to changes in road conditions or traffic signals, thus promoting safety during these critical maneuvers.

In contrast, the other choices, while they might present challenges or conditions that require extra caution, do not inherently necessitate a change in formation for safety. For example, riding in the rain, during group rides, or at night may require increased attention and awareness, but they do not compromise the basic safety protocols of staggered riding as directly as turning does.