The man was believed to be cycling down the hill at around 00:45 when the accident happened.
In an appeal for information, police said he was wearing dark shorts, white trainers and an orange long-sleeved jumper.
He is currently receiving treatment in hospital for his injuries, which are deemed serious.
Anyone with information, or dashcam or doorbell footage, is being asked to phone the police on 612612 or the independent charity Crimestoppers anonymously on 0800 555 111 or via their anonymous online form at crimestoppers.uk.org, quoting police reference number M04060/2024.