A SOCIAL afternoon for a group of Bendigo work colleagues ended with four women airlifted to hospital after their bus crashed and rolled at Maiden Gully.Thirteen people were on board the 26-seater Bendigo Bus Co coach when it was involved in a collision with a black car on the Calder Highway just outside Bendigo shortly after 5pm.Two women were pinned under the bus while other passengers were trapped inside.A 33-year-old woman was flown to The Alfred with neck and spinal injuries while a 57-year-old woman was flown to the Royal Melbourne Hospital where she is in a serious condition in intensive care with neck, spinal and leg injuries.Fourteen patients were transferred to Bendigo but two were airlifted to the Austin Hospital later in the night, one woman with multiple leg fractures and another with leg and back injuries.Acting Senior Sergeant Geoff Owen said preliminary investigations into the cause of the crash were under way.He said the car had been travelling along the Calder Highway toward Marong while the bus was travelling between Hermitage and Monsants Roads, across the highway.“I wouldn’t speculate to the cause or who was at fault.”Maiden Gully couple Tom Stewart and Christine Howard were first on the scene and immediately suspected the worst.“My wife heard an almighty bang ... she looked out the window and said ‘oh my God ring 000’,” Mr Stewart said.“I raced over and could straight away see there was at least one person trapped.“There was hardly a murmur from inside. I thought they’d been killed.”Mr Stewart described the offset intersection of Monsants and Hermitage Roads with the highway as “treacherous” while Ms Howard said the crash was an example of the need for seat belts to be mandatory on all busses.“I hope they had seatbelts on – this should be a call for seatbelts,” she said. “It can make such a difference.”SES Incident Controller Bridget Hague said crews from Bendigo, Marong and Castlemaine responded and lifted the bus to free the trapped passengers.The Calder Highway was re-opened to traffic about 8pm.