A bus driver is in a critical condition after being run over by his own bus outside Waikato Hospital in Hamilton this morning.

Sergeant Craig Taylor said emergency services were called to the main entrance to the hospital's car park about 9.15am.

"It appears a bus driver has parked his bus with the vehicle in gear and the bus has moved forward," he said.

The Orbiter bus rolled about 40 metres from a bus stop outside the hospital's main entrance before crashing a pedestrian crossing pole and a give way sign.

There were no passengers on board.

"Attempting to stop it the 52-year-old man was run over by the bus and suffered critical injuries. He is now in the hospital's Intensive Care Unit."

Fire and ambulance officers were at the scene within minutes and took the man to the hospital's intensive care unit.

Serious Crash Unit and Commercial Vehicle Investigation Unit staff were at the scene, Mr Taylor said.

He said hospital staff and kaumatua were blessing the site and the bus was being removed.