Traffic was brought to a brief standstill for Furness commuters when a Volkswagen car caught fire on the A590, just outside Lindal.
Emergency crews were alerted around 4.43pm and were quick to the scene.
It has emerged a VW Golf driven by a woman began to smoke.
It was stopped in a lay by before bursting into flames shortly afterwards.
Paul Milburn, of Barrow Fire, confirmed the incident was not being treated as suspicious, and appears to have been an accident.
He said: “We managed to contain it within 30 minutes.
“We needed two fire engines to increase our water supply.
“We used two breathing apparatus and a jet hose reel to extinguish it.
“There was a lot of flammable material inside the car.”
With car fires able to burn at more than 800 degrees celsius firefighters were forced to take extreme precaution when tackling the blaze.
Police cordoned off the area, reducing the carriageway to just one lane as the fire was beaten back.
A spokesman for Cumbria Police also confirmed water which had run off the fire site into the nearby beck would be dealt with by officers from the Environment Agency in the coming days, to ensure no contamination had taken place.
The road was reopened to the public after being partially closed for roughly three hours.
Jamie Coward, station manager at Barrow Fire Station, said: “It’s extremely dangerous, not just the fire, but the plastic fumes and everything else which is given off.
“We always tackle car fires in breathing apparatus.”
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