Alexandra Police are praising quick-thinking members of the public who saved a man after he drove into Lake Dunstan tonight.

The man was driving along State Highway 8 towards Cromwell when he went off the road and into the water about 5.15pm.

Members of the public who saw the accident unfold raced to the man's aid and helped him get out of the vehicle and lake.

Constable Leon Burdett said the public did a wonderful job helping the man escape before emergency services arrived.

"I'd just really like to thank the group who rushed to the man's aid and got him out of the lake, we're really grateful," he said.

The man, in his 60s, was taken to Dunstan Hospital in a serious condition.

The ute he was driving has since been removed from Lake Dunstan and an investigation into the cause of the crash is underway.

Meanwhile, Canterbury emergency services have responded to two separate motor vehicle accidents this evening - both involving motorbikes.

Police are currently attending a serious crash between a motorbike and car at the intersection of Poyntzs Rd and South Eyre Rd near Eyrewell Forest.

A spokesperson said they were called to the scene at 8pm and the intersection remained closed.

A St John spokesman said one patient was being transported to Christchurch Hospital in a serious condition.

Elsewhere one patient was being flown to Christchurch Hospital in a serious condition after a motorcyclist crashed into a bank near Hurunui.

The incident occurred on Dommett Rd, part of State Highway 1 in Canterbury.

Six people have died on the country's roads in the last two days, bringing the road toll to 246 for the year to date.

Annual road deaths in New Zealand increased from 253 in 2013 to 380 last year.

The number of serious injuries jumped from 2788 to 3264 per year over the same period.