The British Horse Society (BHS) says it received more than 2,000 reports of what it termed ‘road incidents’ in the last six years.
According to the society, 181 horses died at the scene of those incidents - or were ‘put down’ afterwards.
A spokesman for the society said: “Last year, the British Horse Society launched its ‘Dead, or Dead Slow?’ campaign after shocking statistics revealed the threat that horse riders face on our roads.
“The aim of the campaign is to educate drivers on how to safely pass a horse and it continues to be a huge success.
“In the latest report from the BHS there were over 2,000 reports of road incidents involving horses, with 181 horses dying at the scene or euthanised.
“The BHS encourages horse riders to wear hi-viz gear at all times on the road - even in bright sunlight it can be hard for a driver to see a horse.”
Alan Hiscox, British Horse Society director of safety, added: “We are asking drivers to slow down to 15mph when they see a horse on the road.
“A lot of people aren’t sure how to safely pass a horse when driving and that is why we are working towards strengthening the Highway Code so that all drivers know they should slow to 15mph when they meet a horse on the road.”