n. An inadvertent traffic-calming device created by piles of snow that extend into the street at the corners of an intersection; a snowy neckdown.
Rather than using up the entire breadth of the road, vehicles tend to take the slowest, most safely navigated route around the corners of a slippery intersection. When snow-ploughs clear roads, they leave large piles at roadsides and junctions, which vehicles must drive around. Finally, pedestrians also tread their own optimal paths through the snow. The result is the type of snowy neckdown, or "sneckdown", shown in the photo.
—“Undriven snow,” The Economist, February 13, 2014
A video he made a few years ago illustrating these natural neckdowns continues to grow in popularity, especially after a storm. This January accounts for almost 20% of the video's views. Now, fans of his work have coined the Twitter hashtag #sneckdown — a shorter version of snowy neckdown.
—Kate Dailey, “Sneckdown: Using snow to design safer streets,” BBC News, January 21, 2014
2014 (earliest)
@BrooklynSpoke @HildaBikes @benkint @Streetfilms #sneckdown
—Aaron Naparstek, “#sneckdown,” Twitter, January 02, 2014
The Twitter thread in which the #sneckdown hashtag was coined: