A cyclist was more than three times the legal blood alcohol limit for motorists when she rode off the edge of a street and down a bank, suffering fatal head injuries, a coroner has found.

Diana Jane Perriton, 50, and her partner, William Thomas Barnsdale, had been whitebaiting in a lagoon in Westport last September 8.

Mr Barnsdale told Hastings coroner Christopher Devonport that each had consumed a water bottle full of white wine before they cycled onto a causeway next to the wharf, 1.5m above Gladstone St.

Ms Perriton, who was cycling about 5m ahead of him "then rode straight over the edge".

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"She went straight over and landed on her head. She was wearing a helmet," he said.

Witness Jadelena Rule said she hear a "clink" noise and saw Ms Perriton flip "with her white gumboots going in the air".

"There was another bang. I think it was her bike hitting the ground."

When Ms Rule looked over the edge she saw the bike in the middle of the road some distance from Ms Perriton.

"When I looked over I saw the bike helmet sitting on the road near her feet."

But another witness, Debbie Archibald, said she was fairly sure Ms Perriton had not been wearing a helmet.

Ms Perriton was first taken to Westport Hospital but it was decided she should be transported to Christchurch.

She died in the helicopter en route.

A post mortem found that she had 257mg of alcohol per 100ml of blood - the legal blood alcohol limit for drivers over 20 is 80mg.

Pathologist Martin Sage said there was no apparent strap burn or abrasion under the chin or on the sides of the neck, which would have indicated a helmet was worn.

If she was wearing a helmet, Dr Sage considered it was not adequately secured to provide protection and came off in the crash.

In his report, released today, Coroner Devonport said the crash did not appear to have been caused by the actions or inaction of any other person.

The high blood alcohol level in Ms Perriton's body was likely to have affected her judgement and impaired her ability to control her bicycle and her reactions, and was likely to have been a factor, he said.