A council worker suffered serious personal injury when she was thrown from a tractor as it overturned.
The 51 year-old worker, from Bristol, broke her pelvis and badly damaged an Achilles tendon in the incident in NethamPark.
She remained off work for a year but has since returned to an office job.
Bristol City Council has now been fined £20,000 following an investigation by the Health and Safety Executive (HSE).
Bristol Magistrates Court was told the park keeper, who was carrying out maintenance work, was driving the tractor with a trailer attached and had braked as the tractor descended a slope.
The vehicle skidded and she turned to avoid a fence but it overturned, throwing her from the seat.
HSE found the tractor was not fitted with a seat belt or any type of restraint and the council failed to ensure their employee had received adequate training on the use of the tractor.
Bristol City Council of City Hall, College Green, Bristol, was also ordered to pay £4,700 in costs after admitting two breaches of the Provision and Use of Work Equipment Regulations 1998.
HSE inspector Kate Leftly, said: “This incident was entirely preventable and has caused the worker considerable suffering and distress. She had trained three years for her park keeper role but is now office-bound and will need further surgery on the tendon requiring a 12-18 month recovery.
“Every year, there are accidents involving transport in the workplace, some of which result in people being injured or even killed. People fall from vehicles, are knocked down, run over, or crushed against fixed parts, plant and trailers.
“Bristol City Council had inadequate systems in place to ensure operators were suitably trained in the use of this equipment and failed to identify the need for a suitable seat restraint.”