A woman is in a critical condition in ICU after falling out of a moving campervan onto the Waikato Expressway.
Emergency services were called to the scene near Tamahere just after 11am.
The woman had been travelling as a passenger with her husband when she reached around to try shut a door that had not been closed properly.
In the process, she lost her footing and fell out.
Senior Sergeant Rupert Friend said anyone with car issues should pull over before attempting to fix it.
"Certainly our recommendation is that anybody who thinks there's an issue with their vehicle should stop in a safe location before attempting to figure out what the problem is, or fix it.
"But yes, they were travelling along the road at a reasonable speed when it occurred.
The injured woman was taken to Waikato Hospital. The southbound left-hand lane was closed and the serious crash unit is investigating.