The Lincolnshire and Nottinghamshire Air Ambulance attended 59 horse riding incidents in 2002. (7% of all callouts for the year)
Such incidents require extreme caution in approach due the potential for generating more casualties.
Also much of the operating area is rural; there are hundreds of bridle- ways and riding schools in the area. The potential to spook horses, when landing on any callout, is high.
Crashondeck; air ambulances in the UK have no exemption from the 500ft (5-1-e) rule.