Definition: Twilight (or unknown)
As reported by the police or other authorities.
A residual category covering cases where daylight conditions were very poor or where no information on light conditions was available.
This definition is identical in the third and fourth version of the Transport Glossary.
International Transport Forum, Eurostat, United Nations Economic Commission for Europe (UNECE), "Illustrated Glossary for Transport Statistics", 4th Edition, Luxembourg 2009