A fourth man was critically ill in hospital after being cut from the wreckage by firemen.
An AA survey last week described the section of motorway at Iver, Buckinghamshire, as the most dangerous place to drive in Europe.
The lorry, carrying 25 tons of powdered milk, careered off the road and hit a Ford Sierra which had pulled up on the hard shoulder because of a puncture.
The car was flattened and two of the men inside were killed instantly. A third man died as ambulancemen and a doctor battled to free him.
Ambulancemen from three counties raced to the scene and managed to free the fourth man, who suffered severe leg and chest injuries.
Local emergency GP Stephen Vaughan-Smith performed a roadside operation to drain the victim's chest of blood and fluid before he was rushed to hospital.
The crash caused chaos, with traffic jams up to 15 miles long in both directions.
The lorry driver, from Chelmsford, Essex, was arrested at the side of the motorway on suspicion of causing death by dangerous driving.
She was taken to Slough police station but later released on bail. Inspector Paul Kirby said: 'The driver of the lorry will be interviewed within the next two weeks - at the moment she is too shocked to talk to us.'
The four men in the Sierra were believed to be heading from Newbury, Berkshire, to a business meeting.
The accident happened at about 4.20am, just a short while after the stricken Sierra had pulled off the road.
The articulated lorry crashed into the car and jacknifed and its container flew off, landing about 50 yards up the road.
Safety experts yesterday warned of the potentially lethal consequences motorists face by staying in their cars when they break down on the hard shoulder of a motorway.
Sally Warburton, of the Automobile Association, said one in eight motorway deaths occurred on the hard shoulder.
She said: 'It is an extremely vulnerable and dangerous place to be. Every year drivers are killed as they wait for help or try to change a tyre. Many of those deaths could be avoided.
'Our advice is to get off the motorway if at all possible - try to nurse the car to a service station or a minor road.
'If it is essential to stop on the hard shoulder, pull as far over as possible, get out on the passenger side and sit on the embankment away from the car.
'We don't advise drivers to change wheels on the offside of their car. Call the police or a breakdown service and then leave it to the experts.'
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