What happens if a driving journey begins away from a road?

When a journey begins away from a road, we 'snap' to the nearest road node, while applying a time penalty for doing so.

The maximum 'snapping distance' is 1km, and the time penalty applied is the time it would take to walk the snapping distance.

Roads where walking is not allowed (e.g a motorway) cannot be snapped to, as a driving journey could not begin there.