A woman is in a stable condition after suffering serious head injuries in a crash with another cyclist on Victoria Avenue.
It happened at high tide during Storm Eunice, with waves crashing over the sea walls.
Ambulance crews were called to the crash on the cycle track, near lay-by three, at around 7:30pm on Thursday 17 February.
The injured woman, who is in her 50s, was taken to A&E and then transported to Southampton Hospital for treatment.
Jersey Police say she's receiving 'ongoing support'.
The other cyclist was treated at the scene for minor injuries and didn't need to go to hospital.
Officers want to speak to anyone who saw what happened or who may have helped the two cyclists.
Anyone with information is asked to call police on 612612, quoting M01123/2022.
Haut Du Mont Trial: 'It could explode', jury hears 999 calls
Haut Du Mont Trial: Worker checking gas valves spent almost 'entire' time on his phone
Red Arrows still expected for Jersey Air Show
Haut Du Mont Trial: Gas works were 'sloppy, unsafe, and cut corners', allege prosecutors
26 Victoria Village homes get planning permission
Haut du Mont trial: Explosion 'an incident waiting to happen'
Jersey flights impacted by UK air traffic control issue
Engine fault sees private jet diverted to Guernsey Airport
