A methodology is described that enables to use safety management audit assessments and safety culture questionnaire results for estimating the reductions in the reliability of safety barriers in major hazard plants. The critical issue is the establishment of weight factors in combination with the anchoring of "good" safety management. A method is proposed to derive weight factors from statistical accident analysis in combination with a statistical analysis of safety management assessments at a representative sample of major hazard industries. A preliminary set of weight factors is presented with some examples of resulting reductions in reliability-this demonstration confirms that the set of weight factors needs further development. (C) 2005 Elsevier B.V. All rights reserved.