A nasty
road and
sidewalk hazard that develops in the
late fall or
early spring in the
cooler parts of the world. Rain falls on
cold asphalt and
freezes where it hits, somewhat
slowly so that no
air bubbles are trapped in the
ice.
This ice is extremely slick, yet almost invisible. During the day, it appears on the road as a darker patch of concrete. During the night, it does not reflect your headlights, hence the name black ice. Slipping on a patch while walking is an easy way to get a concussion, or worse.