One of Spooking: Horses at Risk's entries is duplicated and credited here:
An interesting on line article called Spooking Car Accidents discusses car accidents and insurance claims related to horses spooking. The article states that according to statistics in the United States, 85% of all car crashes involving horses occur as a result of spooking. Spooking refers to an incident where a horse is alarmed by some sudden change in the external environment such as a car horn, a pedestrian dashing across the road, or a loud noise from a construction site.
The article continues -- “When spooked the horse will panic and behave unpredictably, often leading it to lash out or bolt. There have been numerous cases in recent years of horses spooking which have led to car accidents. A number of these cases have resulted in fatal accidents, while many more have caused serious personal injuries.
The same US study reports that in cases where a horse has spooked in an urban or town environment, 70% of the time it has led to a person suffering serious personal injury, while 22% of the time it has resulted in a fatal car accident. Both London and Paris have recently banned the use of horse-drawn vehicles because of the risk of car crashes.
Another major factor behind these bans has been a regulatory fear of compensation claims. As car accidents involving horses result in such a high proportion of serious personal injuries and deaths, the use of horses in cities opens up both the councils and the companies using the horses to potentially costly personal injury compensation claims."