The overall objective of the Helicopter Safety Study 3 (HSS-3) is to contribute to improved safety in helicopter transport of personnel to, and from, fixed and floating oil- and gas installations on the Norwegian Continental Shelf (NCS). The study is a follow-up of the previous studies Helicopter Safety Study (HSS-1) and Helicopter Safety Study 2 (HSS-2). The HSS-3 main report describes a method for risk quantification, development for the periods 1999–2009 and trends 2010–2019, plus statistical/historical data and the estimation of risk levels. In addition, the study includes an analysis of passengers' risk perception regarding offshore helicopter transport, and a proposal on how the safety can be followed by a set of lagging and leading indicators to monitor safety. Finally, recommendations are given for a number of measures about how safety can be improved or, as minimum, be maintained at the present level. A separate appendix report contains background material for the study.