The Institute of Advanced Motorcyclists (IAM) have published rider attitudes towards their advanced riding course
From the 3,338 respondents, over 90% said that the test had a permanent and positive effect on their riding skills, increased their enjoyment and made them safer riders. Awareness of hazards, conditions, pedestrians and cyclists had also increased and 61% stated that they had avoided being involved in an accident after taking the test.
http://www.iam.org.uk/images/stories/policy-research/evaluation-adv-motorcycling.pdf