Reckless driving by an autorickshaw driver left a 55-year-old woman critically injured and alleged negligence by doctors in a state-run hospital snuffed out her chances of survival in a tragedy that played out on Wednesday afternoon.

Life ebbed from Purnima Ghosh, a resident of Kalyani in Nadia, as she lay at NRS Medical College and Hospital without treatment for one-and-a-half hours after the accident at Narkeldanga around 4.15pm on Wednesday, her son Subhojit alleged.

She and her 19-year-old son were among five passengers in the autorickshaw that overturned when its driver dangerously overtook another vehicle, only to turn on its side while trying to avoid a taxi coming from the opposite direction.

Purnima ended up with several smashed ribs that punctured her right lung, doctors said. She died at Belle Vue Clinic in the evening.

"The accident occurred barely a couple of minutes after we boarded the auto. The driver was speeding to overtake another vehicle. Our auto swerved to avoid colliding with a taxi and then toppled over," recounted Subhojit, who is preparing for the joint engineering and medical entrance examinations.

"All of us fell on my mother and the auto was over us. The people who had gathered there rescued us out one by one. My mother was the last passenger to be pulled out."

The accident occurred near the canal bridge at the crossing of MN Chatterjee Street and Raja Dinendra Street. "This route leading to Sealdah is notorious for reckless driving by auto drivers who overtake at will and don't pay heed to traffic signals," a resident of Narkeldanga said.

The number of passengers on the auto - two in front with the driver and three at the back - was one more than permitted, common across the city where three-wheelers are among the preferred modes of transport.

Purnima and her son were seated side by side to the left of the driver when the accident happened. Mother and son had boarded the auto at Phoolbagan to reach Sealdah, from where they were to take a train back to Kalyani.

At NRS, Purnima allegedly didn't get any medical attention other than two injections - a painkiller and a tetanus shot.

"There were only junior doctors around and they administered two injections, saying that the pain my mother was in would subside within half an hour. But she continued to have chest pain and had difficulty breathing, too," said Subhojit, who took his mother to Belle Vue Clinic on seeing her condition worsen in the 90 minutes she was at NRS Medical College and Hospital.

Subhojit's maternal uncle, who had reached the hospital by then, was apparently the first to suspect that the Purnima had broken her ribs. "When I tried to feel her ribs, my fingers seemed to be sinking in," the 19-year-old said.

Doctors in the emergency ward of NRS had advised a chest X-ray, for which she needed to be taken to another block of the hospital in a trolley stretcher or a wheelchair.

"A wheelchair wasn't available; so how was I to take her there to get the X-ray done? Relatives of some of the other patients asked me to carry my mother in my arms. But it was impossible to lift her because of her condition," Subhojit said.

Around 6pm, Subhojit and his maternal uncle hired a taxi to take Purnima to Belle Vue Clinic, on Loudon Street. Doctors there said the 55-year-old's condition was already very critical when she was brought in.

"The patient was in agony and could hardly breathe. She had low blood pressure and a high pulse rate. It was apparent that she had multiple fractures of the rib cage," said Saurav Das, emergency medical officer at Belle Vue.

A chest X-Ray confirmed the diagnosis. The medical team suspected abdominal injuries, too, but Purnima went into cardiac arrest before they could treat her for that. She was put on a ventilator but she died at 9.55pm.

Purnima's fractured ribs had punctured her right lung, but the left lung was intact and that kept her breathing for some time.

"A punctured lung leads to presence of air in the cavity between the lungs and the chest wall, a condition called pneumothorax. This causes the damaged lung to collapse. A patient can breathe from the other lung, but needs immediate medical intervention to survive," said critical care expert Ajoy Sarkar.

According to him, Purnima possibly died because of hemopneumothorax, a condition in which blood fills up the chest cavity when a lung is punctured, leading to this vital organ collapsing.

The cause of death given by the hospital is: "Pneumothorax with acute contusional lung injury in a case of polytrauma."

Officials at NRS said on Thursday that they hadn't received any complaint from the patient's family and so couldn't comment on whether there had been any negligence.

One senior official contested Subhojit's allegation that there was no wheelchair or trolley stretcher in the emergency ward when Purnima needed to be taken for a chest X-ray. "We have 20 trolleys and an equal number of wheelchairs on every floor. There is no shortage," he said.

In February, Moubani Rej, a 16-year-old schoolgirl on her way to a Madhyamik examination centre near Kidderpore had her right hand severely injured when the auto she was in rammed into another .

The auto driver was never arrested. The police said they could not trace him without the auto's registration number despite speaking to several unions.

The auto driver responsible for Purnima's fatal injuries hasn't been traced either, although the police have seized his vehicle, which he had deserted after the accident.

Sources in the traffic police department said sergeants had been asked to be extra vigilant about autos carrying more than the permitted number of passengers across some of the busier routes of north Calcutta, including Sealdah-Beleghata, Ultadangaga-Bicholi Ghat and Ultadanga-Karunamoyee.