Doh, leading a group ride this sunday made the stupid mistake of using a bridleway with blind corners which is usually very quite but of course it's blackberry picking session.
Coming round one of the corners there were two pickers/walkers in the way – we all managed to stop and they had moved out the way but it's not the best advertisement for responsible riding.
Reflecting on it the biggest issue is the potential stack towards the rear of a group of riders. The walkers did not say anything but if I had been in their position I would not have been impressed. Lesson learnt – slow for blind corners and keep group rides on as much open trail as possible.
At 10mph a bike travels 4.4 metres in a second so given 0.5 seconds reaction time that equals 2.2 metres plus braking time. Not an expert but it looks to me that a bike stops in something like 4 metres or two bike lengths. A car travelling at 20mph (perceived as slow to most walkers) needs 12 metres. So a farmers Land Rover is likely to represent more risk to the average walker.