A sneckdown (or snowy neckdown) is a buildup of snow on a road that has not been flattened and cleared by traffic, particularly at an intersection. Because it marks where traffic does not go, a sneckdown may reveal where traffic calming measures such as curb extensions or narrower lanes might be safely implemented.^[1]

The term "sneckdown" was coined by Streetsblog founder Aaron Naparstek in 2014,^[2][3] popularized by Streetfilms director Clarence Eckerson, Jr. and spread widely via social media.^[4] Other Twitter hashtags that have been used to describe snow-based traffic-calming measures include #plowza, #slushdown, #snovered and #snowspace.^[5]

The practice of using snow to trace the behavior of vehicles, pedestrians, and playing children was already described in Camillo Sitte's 1889 urban design treatise The Art of Building Cities.^[6]

In the 1980s, some planners in Australia distributed cake flour in intersections to observe patterns of vehicle movement hours later.^[5]

In Philadelphia, Pennsylvania, United States at Baltimore and 48th Street, a sneckdown-inspired permanent upgrade to the pedestrian environment was made in 2011.^[7]

• Desire path
• Tactical urbanism

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• Undriven Snow The Economist
• Sneckdown: Using Snow to Design Safer Streets BBC
• What the Heck is a Sneckdown? Treehugger
• 2014's Endless Snow Has at Least Been Good for Transportation Nerds Atlantic Cities
• "Sneckdowns" Reveal the Street Space Cars Don't Use Greater Greater Washington
• Sneckdowns: How snowstorms can teach us to build smarter roads The Week
• The 'sneckdown': Nature's pedestrian island WPIX11 News NYC