West Midlands Ambulance Service was called to the A442 Eastern Primary slip road exit for the town centre and railway station at just before 2.45pm.
Two ambulances together with a paramedic support officer in a rapid response vehicle and two Midlands Air Ambulances attended the scene.
Steve Parry, a West Midlands Ambulance Service spokesman, said: "Ambuance crews arrived within minutes of the incident to find a car significantly damaged after colliding with a bus on the slip road exit of the A442.
"The driver of the car, a woman believed to be in her fifties, was treated for serious head, chest, lower leg and pelvic injuries.
"The patient was trapped in her vehicle which was extensively damaged. She was anesthetised by a doctor before being immobilised with the use of a pelvic binder, neck collar and spinal board.
"The patient was airlifted to the Queen Elizabeth Hospital in Birmingham where the trauma team were alerted to the serious condition of the patient."
Kieren Bodill, spokesman for West Mercia Police said a woman received "serious" and "potentially life threatening injuries" in the smash.
The crash took place between a Vauxhall Corsa and a bus and the car ended up partially under the bus, Mr Bodill said.
The injured woman was the driver of the car.
Officers said they believed her to be aged between her late 30s and 40s.
No passengers on the bus were injured.
Road closures remain in place at Hollinswood southbound on the A442.