It has become a necessity, in light of the increasing number of horses being spooked on the Taieri by drivers travelling too fast and too close.
And Jess (17) believes it is only a matter of time before someone is seriously injured.
"I'm surprised I haven't been hurt yet."
She said Johnny - her 20-year-old advanced dressage horse - was used to vehicles on open roads.
But he was spooked recently when a bus passed them so closely that her riding crop scraped along the side of the vehicle.
"If I can hear a vehicle coming and it's not slowing down, I gesture with my hand for them to slow down. They seldom take notice."
She said there had been occasions when a car had slowed down to pass her, and another car behind had pulled out and passed both her and the first car.
"I've even been yelled at by a driver to get off the road."
Jess's mother, Tania McMillan, said her daughter had been lucky to date.
A family friend was not so lucky recently when he was passed by two large trucks which spooked his horse.
He was thrown from the horse, which bolted, and he fell into a ditch.
"A kid on a bike is unpredictable. A horse is a thousand times more unpredictable. It can move a great distance in a very short time.
"If a big truck goes past at 80kmh, it's like throwing a hand grenade."
Mrs McMillan had witnessed many "dangerous" incidents over the past year while following her daughter, and believed many of the dangerous and inconsiderate drivers were those in service vehicles, vans and trucks.
She was now taking note of the company vehicles involved.
"It's a driver education thing. I'm sure people don't mean to be dangerous."
There is no legal speed for passing horses and their riders. However, Police Senior Sergeant Ed Baker, of Dunedin, said people were required to drive considerately and to the conditions of the road.
"One of the conditions could be that a horse is on the road.
"You should take the same precautions passing a horse and its rider as you would driving past a small child standing on the side of the road."
Mrs McMillan said a safe and considerate way to pass horses and their riders was to give them a wide berth and drive at about 30kmh.
