The grieving widow of the victim of an alleged drink-driver has lashed out at the law that allows an accused motorist back behind the wheel less than a month after the accident.

New father Frank van Kampen, 46, died after 70-year-old Alison Downer allegedly hit him while he was cycling along State Highway 1 between Otaki and Waikanae.

Downer - who is reputed in the community to have a long-standing drinking problem - failed a police breath test after the September 18 crash.

Downer's licence was immediately suspended for 28 days, but under existing drink-driving laws she is free to drive again as no charges have yet been laid against her.

Talking exclusively to the Herald on Sunday, van Kampen's widow Jude Pauwels said she was "terrified" for her family's safety now that Downer was back behind the wheel.

She said she had been told that Downer had been seen driving around town.

Downer did not respond to calls and her lawyer, Sandy Baigent, declined to comment. But a family friend said she had "definitely not" got her licence back yet, and had not been driving in the past month.

Police said their investigation of the crash continued but would not say when charges could be laid.

Jude Pauwels had phoned police to see what she could do to stop Downer from getting her licence back, she said, but was told Downer would receive it this weekend.

The fact the elderly woman was legally allowed to drive again was "ludicrous", Pauwels said; the accident had robbed her son Dante, 13, of a stepdad and their new baby Alexandra of her father.

"Even if she doesn't physically have it back right now she is entitled to it and there's nothing I can do to stop her from getting behind the wheel - I'm absolutely devastated and terrified about that," she said.

"I'm outraged that someone can kill the love of my life and 28 days later be back on the road. It's ludicrous.

"Alexandra isn't much more than 10 weeks old but she already knows her dad isn't around and it just guts me."

She is pushing for longer suspension periods for those who are found to be over the legal breath alcohol limit.

"A 28-day suspension is outrageous and dangerous and it's a huge matter of public safety," she said.

"It reflects a significant flaw in the law and that is what needs to be changed.

"I really want to push for people to be aware of that."

Todd McCormack, a former Serious Crash Unit officer who now works as a crash investigator and analyst, said he would like to see recidivist offenders and those who exceed 640 micrograms suspended for more than 28 days.

"Three months would be a better period of suspension for someone like that," he said. "Some investigations can carry on for up to two years and while some people would like to see them suspended the whole time, you've got to find somewhere to draw the line."

Drink-driving law specialist Zahir Mohamed said those who have had their licence suspended must, by law, have it returned to them after 28 days if no charges have been laid.

He said there were many cases where the investigation would continue "for months or even years" before a driver was charged.

To have a licence revoked for 28 days, a driver must have "relevant convictions" in the past four years and be caught drink-driving with a breath alcohol level exceeding the legal limit of 400 micrograms per litre of breath.

A driver can also face an immediate suspension if they are caught with a breath-alcohol concentration above 640 micrograms.

"As soon as those 28 days have passed, and there has been no charges or a conviction, they can be back on the road driving around even if they have drink-driving convictions in the past," Mohamed said. "If the police have handed it to the NZ Transport Agency, you can just go and pick it up.

"It happens in many, many cases that someone won't be convicted for months or years and will be able to drive in that time."

Serious Crash Unit Sergeant Stu Kearns said the 28-day suspension law was in place because "there has to be a set time". Police were not under pressure to press charges straight away, he said.

"We have to look at all the facts and expert reports, which can take some months. It's not a quick process," he said. "At the end of the day that person could defend it and get off, and we can't keep them suspended for that long.

"And there is always the aspect of being innocent until proven guilty, but I understand that can be very emotive for some people."

Pauwels said she would campaign to extend licence suspension laws and hoped to raise awareness on the topic.

"Nothing will ever make this right and it's a nightmare but I want to try and make a difference, even though nothing is going to bring Frank back."