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
A look ahead at the Bank Holiday forecast for the Border region.
Cumbria County Council will start work on a £320,000 resurfacing scheme on 6 June, between 6.00pm and 12.30am.
ITV Border's favourite Tapir has left the Lake District Wildlife Park near Keswick, to travel to his new home in the United Arab Emirates.