Lizzie Connell was at Newbridge when her Renault Twingo ground to a halt as flames leapt from the bonnet.
The 29-year-old lawyer and her husband Andy scrambled to safety minutes before their car was fully on fire – and then exploded.
Fellow motorists stopped to help amid fears that someone was trapped inside, forcing the Portobello couple to desperately warn them to keep back.
Mrs Connell said: “At first I thought I was in the wrong gear but I wasn’t.
“The car ground to a halt and lost all power. I tried to start it a couple of times but it didn’t work.
“My husband noticed that there was a wee flame coming out of the bonnet and shouted ‘Get out of the car and run!’.
“We escaped just in time. I saw at least one brave person get very close to the vehicle, so I shouted to them that it was my car.”
The pair took refuge on the roundabout but were later forced to cross the busy road to reach a safe distance as the flames leapt higher, sending a column of thick black smoke into the sky.
It took fire crews more than ten minutes to arrive as traffic – including an oil tanker – passed within feet of the burning car.
The couple, who had been en route to a falconry display, heard a series of bangs as the windows “exploded” and the car was consumed.
Alex Cole-Hamilton, Lib Dem MSP for Edinburgh Western, said: “This is an incredibly busy roundabout at all times of day, and the fact that somebody wasn’t hurt is a miracle.”
The incident, which happened last Sunday morning, has been reported to Renault, which looks set to begin its investigation into the cause of the fire next month.
A spokesman for Renault said the company treated all safety-related incidents “seriously”.
He added: “We have been in touch with the customer who first reported the incident to us on Monday.
“We have informed the customer that we would be arranging for one of our technical inspectors to inspect the vehicle – this is in the process of being arranged with the customer and should be completed within two weeks.
“Until the inspection report is complete we are not able to offer any further comment as we have not inspected the vehicle.
“We will remain in close contact with the customer until the incident is resolved.”
Firefighters from South Queensferry with breathing masks used two hose-reel jets to extinguish the fire and the road was closed for more than an hour for the clear-up.
The roundabout – where the M8 meets the M9, the A89 and the A8 – is among the busiest road junctions in eastern Scotland, also catering for traffic heading to and from Edinburgh Airport.