This paper describes the methodology and the results obtained in the framework of the NEEDS (New Energy Externalities Developments for Sustainability) European project, while evaluating externalities due to accidental situations. In particular it focuses on the results obtained from a risk assessment of hydrogen transportation technologies. The quantification of risk as an additional source of externality to the cost of transporting hydrogen was obtained with the support of a commercial numerical simulation software that was specifically designed to deal with hazards in process industry environment. A number of scenarios and site dependencies have been taken into account in order to assess the risk associated with different transportation means, under several accidental conditions (e.g., kind of rupture and weather conditions). Results were compared with social acceptability limits of risk set by some countries. (C) 2009 Elsevier Ltd. All rights reserved.