This matches my experience on shared pedestrian / bicycles low density roads in countryside. 30 km/h (a little less than 20 mph) is the limit between okish and

This matches my experience on shared pedestrian / bicycles low density roads in countryside. 30 km/h (a little less than 20 mph) is the limit between okish and dangerous. Actually pedestrians start to worry a little before that speed but of course half of them don't see the bicycle approaching. The cyclist see them a long time before overtaking and assesses whether they are safe to pass or require a slow down.