These were the dramatic scenes today as flames engulfed a bus that had been travelling down the M4.
No passengers were hurt in the fire, which happened at the busiest point of the rush hour, closing two lanes of the eastbound motorway between Cardiff and Newport at around 5.40pm.
Thousands of commuters were forced to wait as emergency services rushed to the scene.
Eyewitnesses reported seeing flames licking the bus and a huge column of smoke billowing up into the sky.
It is understood the bus’ driver pulled over onto the hard shoulder and passengers were able to escape, gathering 50m away behind a motorway barrier.
Rachel Reynolds, 33, of Pentwyn, Cardiff, was a passenger on her way home from a picnic in the sunshine at Tredegar Park when she took this remarkable picture of the blazing bus on her phone.
She said: “We were travelling back to Cardiff at around 6pm after a visit to Tredegar Park for a picnic.
“As soon as we got onto the M4 at J28 the traffic was unusually heavy and slow moving and you could immediately see smoke billowing over the M4 in the distance.
“There was so much smoke we thought a building must have been on fire but as we got closer we firstly saw all the passengers safely at the side of the road and then we approached the bus, the whole of which was on fire.
“A fire engine was already at the scene with another rushing down the M4 to provide further assistance.”
Another witness, Matthew Muir, said he thought the bus might have overheated and pulled onto the hard shoulder.
“A service bus engine must of overheated and caught on fire due to the heat, all passengers were off by the looks of it,” he said.
“They were standing behind the crash barriers about 50 metres away from the bus.”
Chris Lewis, who also drove past the bus as it was burning, said it was the worst fire he had seen, “in 11 years of commuting on the M4”.
South Wales Fire and Rescue Service said it was called at around 5.40pm after the bus caught fire between junctions 28 and 29, where the A48 leaves the motorway for Cardiff.
A spokesman said all passengers had left the bus safely and there were no reports of any injuries. The motorway lanes later reopened.