A group responsible for managing the Epsom Downs is stepping up its "policing" of the rules after a rise in the number of dogs chasing racehorses.
The horses are trained on the Downs every morning with dog owners told to keep their pets restrained on a lead.
Nick Patton, the Jockey Club's training ground manager, said rules were often ignored leading to riders being thrown from "spooked" horses and injured.
The Epsom and Walton Downs Conservators said keepers would be reminding owners.
Mr Patton added helmet cameras for the jockeys and CCTV cameras in the area were being considered.
"We've had notices on the Downs reminding people for a long time that dogs should be properly controlled, but we are putting up newer, more prominent notices," chairman of the Conservators, Liz Frost, said.
A code of conduct reminds dog walkers they "are in danger when in close proximity to racehorses in training".
'Air and exercise'
Training times are 06:15 to midday on Mondays to Saturdays, and between 08:00 and 09:30 on Sundays.
Ms Frost said the Epsom Downs were safeguarded and controlled by an Act of Parliament, which states the public are allowed access "for air and exercise on foot, subject to there not being any interference with the training of racehorses".
"People need to understand that racehorses do take priority during training, and to understand proper control," she added.
"Racehorses are very sensitive creatures - their natural reaction to a dog is to run."
Mr Patton said there had been incidents of dogs running right through the horses, "barking and snapping at their heels", and riders being thrown and suffering injuries ranging from sprained ankles to broken collar bones.
"The horses also gallop across footpaths and roads, injuring themselves and then not being able to race," he said.