My view is you start a race / event to finish it , except in the most difficult conditions where a number of planned escape routes are a back up, and a good level of navigational skill is essential for either scenario.
Sense has to prevail in the worst conditions, I remember some years ago on the Kentmere Horseshoe, snow driving uphill around High Street, a number of us decided to stick together to get down safely, it so happened the best route down was to continue the race.
Only later did we find out there was a fatality, an experienced female runner missed the summit and was brought down later that evening.
No one can afford to take chances with life.