Perception of safety - research ideas, opinions needed!

offering some purely empirical number-based study on whether training courses for adults do or do not reduce the amount of cycling deaths on the road

If you could supply that with a reasonable degree of certainty within the restrictions of an MSc thesis, a lot of people would want to talk to you :)

As I said, your approach depends a great deal on what you want from it. Interested in more accedemia, then sure, you can go more theoretical. Interested in a specific industry or profession, give yourself a tight, original brief you can answer effectively.