Here’s a site that’s new to me – the Road Safety Observatory, which aims to provide ‘key facts and summaries of research on road safety topics’. There’s one page devoted to motorcycles which has a reasonable ‘position statement’ together with a list of references. It’s by no means exhaustive, but it is a good place to start.

http://www.roadsafetyobservatory.com

The Institute of Highway Engineers Motorcycling guidelines are an updated version of a set of award-winning guidelines for highways engineers and road safety professionals originally produced in 2005 and aimed at encouraging greater awareness of the needs of powered two-wheelers and effective interventions to improve safety.

The most recent update reflects changes in policy and advances in technology and knowledge.
http://www.motorcycleguidelines.org.uk/