and a little bit about why it's actually easier for motorists to overtake a group of cyclists 2 abreast rather than single file..
http://ukcyclelaws.blogspot.co.uk/p/the-laws-according-to-highway-code.html
No evidence, 27% of all trips are made by bikes in the Netherlands. The Dutch enjoy the greatest level of safety for cyclists in the world! This is a combined approach of responsibility and infra-structure which has lead to a coexistence of motor vehicles and cyclists.
I would of thought that...