This is one of those MUST READ studies for all safety professionals who deal with machine gaurding and interlocks, and/or have a behavior based safety process! Although the study was done on Computer Numerical Control (CNC) machines in the UK, we can certainly see how the results can be expected on ANY machinery and by ANY worker in any country. Defeating interlocks has been a problem for as long as interlocks have been on this earth; for us to ignore this fact is dangerous! This study, done in the UK on CNC machines, is something we can hang our hat on and begin to understand the mindset so many have when it comes to “acceptable practice”. The current research sought to identify reasons why operatives defeat interlocks on CNC machines, and to obtain an understanding of the extent of this behavior across the UK engineering industry. The findings from this research provided a number of valuable insights about the frequency of defeating interlocks and the influences upon this behavior.