Chief Inspector Kevin Greenhow told ITV Border:
"The event has grown and grown and we're expecting in excess of 40,000 people over the course of the Fair. We're asking motorists throughout the North of England and South Scotland to be aware that there will be carriages and caravans on the road and they must be passed with caution.
Respect other road users and be patient. Last year was successful and safe, let's have the same again this year."
More top news
Cumbria Police are supporting a national campaign to raise awareness of protecting children and young people from child abuse and neglect.
Resurfacing improvements mean a Galashiels road will be closed next month.
Kerrie brings you Sunday's pollen report