Norwegian authorities has a long-term goal to develop the E39 as an improved and continuous Coastal Highway Route between Kristiansand and Trondheim without ferries. New bridge technology needs to be developed for crossing the extreme fiords along the west coast, and the bridges will be exposed to significant ship traffic. The Norwegian Public Roads Administration's (NRPA) handbook for bridge design is not detailed when it comes to execution of ship allision risk assessments. A pragmatic approach is to use a so-called Heinrich-factor to take into account that not all potentially critical allisions will lead to a collapse of the bridge. This factor is used by many consultants and have a large impact on the results in the ship risk assessment; however, there are no mutually agreed understanding of it. This paper examines and discusses whether the Heinrich factor is a reasonable approach and if the assumptions behind it are relevant when designing the large bridges on E39. The paper concludes that the approach has some principal challenges, but that it provides, with some adjustments and clarifications, a reasonable basis for bridge design. It is suggested to change the name to “severity factor”, and specific values for the Bjørnafjord Floating bridge are derived in an expert elicitation process.