# The Railways (Accident Investigation and Reporting) Regulations 2005, Paragraph 1


A collision of rolling stock with an object on or adjacent to a running line which under slightly different conditions might have caused a derailment, except—
(a) if it is notifiable under regulation 4(1);
(b) if the object was an animal; or
(c) where the obstruction was caused by an obvious act of vandalism.

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Source: https://www.legislation.gov.uk/uksi/2005/1992/schedule/2/paragraph/1 (the official version)
Page: https://openlegislation.uk/railways-accident-investigation-and-reporting-regulations-2005/schedule-2/paragraph-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.