The man was thrown to the roadway, suffering serious head and leg injuries.
Officers from Northern Beaches Police Area Command attended and established a crime scene, which was examined by forensic police.
Inquiries into the incident continue.
Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au. Information is treated in strict confidence. The public is reminded not to report crime via NSW Police social media pages.