 Disaster struck the motorcycling in 1911 when T. Henshaw 's bike struck six spectators at around 50 miles per hour ( 80 km / h ) . This left Henshaw with serious fractures and one woman with a severe brain injury . In another incident on 18 May 1959 five people were injured while watching a motorcycling stunt when a 10 @-@ foot ( 3 @.@ 0 m ) wide section of stands collapsed , causing the spectators to fall 15 feet ( 4 @.@ 6 m ) to the ground . 
