A table sent by WA Police yesterday outlined each motorcycle-related death from January 1 to September 14.
It said alcohol was a factor in the crash that killed 22-year-old Ryan Antonelli and 22-year-old passenger Bronwyn Clarke two days ago.
Ms Clarke was the first motorbike passenger to have died in WA this year.
The year’s first fatality happened on January 11, with police ruling reckless riding to be the cause of a crash that killed a 28-year-old man in Hillarys.
On May 27, police said speed was the factor in a crash that killed a 60-year-old man when his motorbike collided with two cars in Padbury.
Police emphasised the suggested cause of each crash could change if new information became known.
There have been 22 deaths from motorcycle crashes in WA this year.