An electrical fault could be the reason a Sussex bus burst into flames on the A23.
Motorists watched in horror as the single-decker caught fire yesterday afternoon.
The driver and a passenger on the Burgess Hill-based Sussex Bus coach managed to escape to safety.
The driver was seen scrambling up the bank of the southbound carriageway at Pyecombe.
Fortunately, there were no other passengers on the bus which was travelling to Brighton to pick up rush-hour commuters.
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Early indications suggested the fire was caused by an electrical fault.
Drivers caught in the chaos got out of their vehicles as the blaze raged.
Terri Hunter, 45, of Brighton, was a passenger in a car which passed the coach just as it burst into flames.
She said: “It was crazy. The coach was totally on fire – the whole inside of the bus was in flames. It was so lucky there was only one passenger on board – if there had been more it would have been terrible.
“Drivers stuck in the jam stood on the bank by the side of the bus.
“There was so much smoke.
“It looked like everyone was all right.
“It looked very dramatic.
“It was really, really bad – I have not seen a fire like that.
“It was bonkers.
“There was thick black smoke across the entire carriageway.”
Crews from East and West Sussex fire and rescue services and Sussex Police attended the fire, which started just three minutes before the end of the firefighters’ strike at 3.57pm.
Motorists faced delays as the south- bound lanes were closed by the emergency services.
Thick smoke billowing across the carriageway also caused disruption for traffic travelling north.
A West Sussex Fire and Rescue spokeswoman confirmed four pumps attended including crews from Henfield, Hurstpierpoint and Haywards Heath.