The underpass has been closed southbound following a five-vehicle crash.
A five-vehicle crash on the A3 at Tolworth caused police to close the road southbound.
There was a diversion in place, with traffic being directed over the underpass, but police have reopened the road.
A Metropolitan Police spokesman said it happened at 4.25pm.
One person was taken to hospital, but their condition is unknown.
Expect continuing delays when travelling in the area into the evening.
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