Traffic leaving the city was brought to a standstill on Wednesday evening after a drain cover became dislodged.
A lane on the westbound carriageway of the A63, between the Humber Bridge and Hallmark hotel, was shut at around 4pm.
Confused drivers on the road speculated on the cause of the closure.
One said: "Cops closed a section off near Ferriby in outside lane, no other cars though. Motorway maintenance just arriving, a problem with road maybe?"
Another said: “Lane two closed westbound under Humber Bridge to Hallmark hotel junction. Not sure why, just police parked up."
Humberside police were at the scene to close the lane as Highways England workers inspected the problem.
A spokeswoman for Highways England said: “A drain cover came loose and so the lane was shut so Highways England workers could inspect it.”
The lane was reopened just before 5pm after road maintenance staff secured the drain cover back into place.
Hours before, at around 12.50pm, Traffic Management System INRIX said workers were in the road attempting to repair a "damaged carriageway".
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However, this was cleared around eight minutes later, according to highways England.
One lane was shut, but this was quickly reopened while the carriageway was repaired.
The incident is the second time in two days motorists leaving Hull have been left at a standstill at rush hour.
On Tuesday, the A63 westbound was partly blocked due to a two vehicle crash.
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