Horse rider fatalities have occurred during the cross‐country phase of three‐day eventing when horses have fallen and landed on their riders. There are safety jackets available for horse riders, which are designed to inflate and offer protection when the rider falls from a horse, but the effectiveness of these ‘air jackets’ against crush injury from a falling horse is not well understood. TRL and British Eventing tested an exemplar air jacket to estimate its protective capacity and provide baseline data on the forces applied by a falling horse. Four tests were performed with an equine cadaver. In two tests, one with an air jacket and one without, the horse was dropped onto an instrumented Hybrid III ATD. In two further tests, the horse was dropped onto an array of 123 load cells with a measurement area of approximately 1 m x 2 m. The results indicated that the air jacket could have a beneficial effect in reducing the likelihood of a severe injury being sustained in an accident where a horse falls on a rider. However, with or without the air jacket, there was a high probability of a severe injury being sustained by a rider in the loading condition created for these tests.