The heavy-goods vehicle crashed at around 3.30pm on Saturday on a section of the A64, North Yorkshire, causing perilous driving conditions as the mashed potato began to swell..
During the spillage North Yorkshire police tweeted: "Sadly the freezing chemicals are not lifting on the A64, despite grit and ploughs. The road remains like an ice rink.
"High Powered hoses are being used by fire service but it remains dangerous to road users and is slow going. We will keep you updated with progress"
A police spokesman said: "Instant mash is covering the road and cars have skidded as a result of the mash swelling up."
The potato was finally cleared off the road hours later and the A64 was fully open at 9.15pm.