So you and the Players are moving fast. They're on their way to investigate some ruin, or explore some place, and on the road they meet ... someone. Something. Only, the moment you announce the encounter, the Players decide to sidestep the whole thing or to hide until it passes.
How do you involve the Adventurers in the encounter without shoehorning them in or railroading them?
Bring in elements, such as hooks and shoves, which draw them in or shove them in the direction you want them