Originally Posted by
kbarch
Or you could do like the NY Cycle club does and use repeats of a well-known circuit as the guide. They use four laps of Central Park (which happens to be 24.4 miles, 1,836'), as the guide to what I'd call the cruising speed with which a rider would be comfortable (rides are advertised according to a combination of paceline skill and speed).
Back when my group was posting club rides to attract possible new members for vetting, we had a 500' sorting hill. We'd all start together and hit the sorting hill after about 3 miles. Our 3 pace leaders would go up it, holding their usual pace, and see who was with them when they paused at a parking lot at the top. That worked well.