unintended sudden event or a series of such incidents involving railway vehicle, causing negative consequences for human health, property or the environment

Serious accident - accident caused by collision, derailment or other similar event:

with at least one fatality or serious injury of at least five or

causing significant damage to the vehicle station, the railway infrastructure or the environment that can be immediately evaluated by a committee examining the case for at least 2 million EUR, with an obvious impact on railway safety regulation or safety management.