Both lanes of the A34 road, west of Kings Worthy, were closed just after 7am yesterday after a van carrying swimming pool chlorine was left on its side after a crash.
The chemical was inside metal drums, none of which leaked after the accident.
Leading firefighter, Andy Weeks, of Winchester Fire Station, said: "If it leaks, this is pretty nasty stuff, but if it's contained, then it's all right. The driver was taken away in an ambulance, but wasn't badly hurt. He was lucky."
The northbound carriageway was closed for 90 minutes while the van was recovered and the southbound lane was shut for an hour.
Police operated diversions and said congestion was not as bad as initially feared.
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