The A47 Acle straight ground to a halt on Tuesday evening because of a horse invasion.
15 escaped horses ran onto the busy road between Norwich and Great Yarmouth, causing police to close it in both directions.
Police said they escaped from a field near Vauxhall Holiday Park on the edge of Yarmouth.
Stranded drivers and passengers have reacted with a mixture of frustration and bemusement, with many taking photographs of the bizarre scene.
The horses were eventually captured and placed in a field two miles away.
The incident happened at about 5.56pm and was over by 6.35pm.
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