What element contributes to a "funnel effect" in a coaster's design?

The concept of a "funnel effect" in roller coaster design is primarily created by circular turns or spirals. When a coaster navigates these curves, the train experiences a change in direction that can amplify sensations of speed and acceleration. This effect is particularly noticeable in tightly configured spirals or circular sections, where the lateral forces on riders are intensified, leading to a feeling of being "drawn in" or "funneled" toward the center of the turn.

In contrast, vertical drops, straight tracks, and speed variations serve different purposes in a coaster's overall experience but do not contribute directly to the funnel effect. Vertical drops create moments of weightlessness and thrill through gravity, while straight tracks offer speed without the additional forces created by turns. Speed variations can add excitement and dynamic elements to the ride but do not inherently create a funnel-like sensation. Thus, circular turns or spirals are the key design elements that give rise to the funnel effect in roller coasters.