Traffic was backed up on Tuesday near Ōhau after the crash.
Smith and Thompson are sharing a hospital room and when they were reunited, after initially being in separate rooms, Thompson proposed to Smith.
“When we first got put in the same room Corey asked me to marry him,” Smith said from her hospital bed.
“We are now engaged. That’s one bit of good news to come out of this.
“He said, ‘I know I can’t get down on my one knee, but will you marry me?’”
Smith and Thompson were heading to Levin to help Thompson’s brother, who had run out of petrol.