A major explosion was narrowly averted after a workman cut through a gas pipe metres from a petrol station.
The workman was using an electric power tool at the time.
Firefighters said it was only luck that sparks did not lead to a disaster.
The incident happened next to the BP service station on the A259 Brighton Road, Worthing, at 12.30pm yesterday.
When fire crews arrived, they quickly realised how dangerous the threat was and closed the road.
Worthing fire station commander Peter Martin said: "It is lucky sparks from the disc-cutter didn't cause an explosion.
"Coupled with being right outside a petrol station, it could have been disastrous. The workman is very lucky he escaped unharmed."
The workman is thought to have been carrying out surface drainage work when he cut through the pipe.
As traffic ground to a halt on the A259, there were major delays in the centre of Worthing and on surrounding roads.
Much of the town was gridlocked as police put diversions in place to move traffic away from the coast.
The A259 was closed for two hours. A spokeswoman for Sussex Police said: "We had a call that contractors had cut through a gas pipe.
"The westbound carriageway of the A259 was closed and diversions put in place.
"The road was able to reopen at 2.29pm and traffic was moving normally by about 2.40pm."
Engineers from Transco were called to repair the damage. A spokesman said engineers could be working throughout last night.
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