Motorists faced four-mile tailbacks after an underground blast closed the A140 in the evening rush hour on Tuesday.
Police, firefighters and UK Power Networks engineers were called to Long Stratton after reports of a loud bang and a blast that blew open a manhole cover.
It happened near to a petrol station forecourt and Stratton Motor Company, which sells Lotus and Aston Martin cars, at around 4pm yesterday.
Police said the manhole cover 'shattered without warning close to the road'.
James Betts, sale manager at Stratton Motor Company, said he heard a loud bang.
Several houses close to the scene were evacuated.
Roger Ranson, who works at an office near to the petrol station, said: 'I was told a policeman saw the manhole cover rise to the height of a dustbin.
'At the time it was quite alarming near a filling station and those expensive Lotus cars.
'It's quite eerie – normally at this time of day the road is quite busy.'
A spokesman from UK Power Networks said engineers investigated a fault on the electricity network.
The road was shut for several hours.
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