The Pass Wide and Slow Campaign, which held 200 similar rides around the country last weekend, encouraged motorists to drive past horses carefully.
“Horses are flight animals,” said organiser Rachel Williams, an Equine Ranger from Burgess Hill.
She said that the slower cars drive past and the more distance they give, the safer it will be for everyone.
“We can see over hedges so we can see whether there’s somebody mowing their lawn or a dog barking,” said Rachel.
“Drivers can’t and a horse will dart sideways if something is upsetting them,” she warned.
“If a car is right next to you you’re going to hit the car,” she added.