Any incentive to employee towards safety programme implementation will help only in the beginning. Later on, they demand more and more which becomes a vicious circle and is like opening so called Pandora's box. If you try increase the standards after attaining and maintaining certain level, you will face resistance from the employees. In fact, as the article says, they may hide the issues and do not report, not only for getting the incentive, but that they may be rebuked by colleagues, if the person is involved/reported accident/near miss and deprived others of the incentives.
http://safetydailyadvisor.blr.com/archive/2011/10/17/safety_management_incentives_pros_cons.aspx#comments?Source=SDF&effort=13