Chief Cam Kenyon said the crash happened when two cars collided at the intersection of West Melton Rd and Hoskyns Rd about 6.30pm on April 26.
In spite of having been trapped, the man had been able to walk out once firefighters freed him from the wreckage.
“He was a very lucky man,” Kenyon said.
St John said it sent two ambulances to the scene.
Paramedics assessed and treated two patients at the scene, one with serious injuries and one with moderate injuries.
Both were transported to Christchurch Hospital.
A police spokesperson said inquiries into the circumstances of the crash are ongoing.
Rolleston firefighters and police also attended a two-car collision about 11am on Edwards Rd on Sunday.
There were no reports of injuries.