Environmental issues such as climate change and scarcity of resources have forced the development of new energy carriers for vehicles. This also means that there will be an increase in the number of vehicles running on these new energy carriers in tunnels and other confined spaces. New energy carriers do not necessarily mean higher risks, but they do represent a new situation and imply new risks. These risks need to be evaluated and considered. The mixture of different energy carriers (flammable liquids, gases lighter than air, gases denser than air, batteries, etc.) can also constitute a risk itself, since there are situations where different safety measures need to be taken depending on the energy carrier used and the scenario in question.
In this paper some selected new energy carriers are described, in terms of trends and properties. Some countries have restrictions on the use of some energy carriers in confined spaces. These restrictions are presented. Vehicles are involved in accidents, so also vehicles running on new energy carriers. Some vehicle fires involving new energy carriers are presented and discussed in the paper. It is important to learn from these accidents. It is also important that safety issues related to the use of new energy carriers in tunnels are considered, investigated and reported. Systems, not only components, need to be tested to study different possible scenarios and to develop models for these scenarios. When the scenarios are described in a representative way, technical safety solutions, mitigations systems, and rescue service tactics can be developed. It is also important to study how the different systems (detection, ventilation, mitigation) interact and how the models should be altered depending on the scenario.