What formation should not be used when entering or exiting a highway while riding in a group?

When entering or exiting a highway while riding in a group, the formation that should not be used is the staggered formation. This is primarily because the staggered formation is designed to maximize the distance between riders, providing individual space and increasing safety while on straight roads. However, during the critical moments of entering or exiting the highway, riders need to maintain closer proximity and coordination to ensure smooth transitions, allowing for better communication and maneuverability.

Using a staggered formation at this point could lead to confusion and potential conflicts, as riders are more likely to have to adjust their positions quickly in reaction to changes in traffic or roadway conditions. Therefore, a single line formation, which keeps all riders aligned and allows for easier navigation through merging lanes, is more appropriate in these scenarios. Other formations, such as circle and parallel, do not provide the necessary structure and spacing required when dealing with entering and exiting highways, making them less effective in maintaining safety and communication.