The brakes are firmly on an environmentalist's food-delivery service after she was caught drink-driving.

Robyn Susan Guyton was so drunk, in fact, that other motorists felt compelled to act, persuading her to pull over on the highway, the Dunedin District Court heard last week.

The Riverton woman, 62, has made headlines over her green initiatives, most recently at the end of last year after she established the "Longwood Loop".

Guyton did a weekly 150km trip through rural Southland in her electric van, collecting and redistributing produce in a bid to rebuild small communities.

But that was jeopardised on April 30 after she set out to see her Dunedin-based daughter, who was leaving the country.

Guyton packed two bottles of wine for the trip, the court heard, and consumed one of them after visiting her sick mother in Henley.

Guyton's erratic driving soon caught the attention of others on the road who gestured for her to stop.

When police arrived, they found her in the driver's seat of the Mazda.

A summary of facts detailed how Guyton was unable to complete a breath test and so was taken to the Dunedin Central Police Station.

There she opted to provide a blood sample.

It was found to contain 206mg of alcohol per 100ml of blood — more than four times the legal limit.

Duty lawyer Steve Turner said Guyton had made "a significant error of judgment" because of various stresses in her life and had since sought to address that.

Community magistrate Simon Heale said it was comforting that the defendant had taken the situation seriously but stressed the potential danger she posed on the road.

"I just want you to think about what occurred. You were so affected by alcohol that other people on the road could tell there was something wrong and they took steps. That's an incredibly unusual set of circumstances," he said.

Guyton was fined $500, ordered to pay court costs $130 and analysts fees of $215.

She was banned from driving for 28 days before the alcohol-interlock licensing provisions apply.