Drove home late evening after visiting family in Slagelse.

Aprx. 3-4 kms off Slagelse, an object moving slowly in from left (south) caught my eye. I (and my girlfriend) observed what seemed to be a triangular shape with 3 (white) downlights in each corner moving (what seemed to be) slowly in a northerly direction.
I stopped the car (incident occuring on the countryside, outside city), and stepped outside, as I could clearly see that this object/craft was not in any sense using "normal" anticollision-lights.
Object moved what seemed to be slowly, and completely noiseless, right over my head, and continued in a northerly direction.
Colour of object seemed to be black or a dark.
I lost visual after 3-5 minutes (the object only using downlights).
As it was dark and the object was completely silent, it is difficult to establish size (either very, very big and "high-level", or smaller "low-level").
My impression was that it was flying low-level, aprx 300-500ft.
Sky was clear, and weather nil.
Witness indicates that the date of the incident may be approximate.  PD