Hull's Daltry Street flyover did not melt during the heat wave, as feared – the surface came unstuck.
Motorists travelling into the city centre noticed bulges and dips in the road.
It was feared, as temperatures hit almost 30C last month, that the road surface had started to melt.
Other parts of the country have reported melted roads this summer – the hottest since 1976.
However, a Highways Agency spokesman said: "Repairs were carried out last week to a surface defect on the A63 Daltry Street flyover in Hull, which was affecting a small section of lane one.
"Engineers investigating the cause of the defect found that the road had not melted.
"There was an area of de-bonding between the waterproof membrane and road surfacing, possibly due to water getting between the layers.
"This allowed the road surface to shift due to the movement of traffic."
