Ambulance service St Johns is urging the government to make wearing seatbelts compulsory on some bus services.
Two people have died and many others have been injured in three separate bus crashes in recent weeks.
The government has now asked the Ministry of Transport and the Transport Agency to investigate the crashes.
Last week road safety advocate Clive Matthews-Wilson said public buses should have seatbelts installed for passengers.
And St Johns' director of clinical operations Norma Lane said the government should be looking at the importance of seatbelts to prevent injuries and fatalities in bus crashes.
She said St John typically responded to around six significant bus crashes each year.
"People losing their lives, losing limbs, fractured limbs, and having to live with life-changing injuries just for the sake of not putting those safety belts on, or that they're not available."
Ms Lane said several overseas countries had regulations around seatbelts on buses, as well as bus monitors who helped encourage children to put their seatbelts on while riding school buses.