Two pedestrians were hit by cars and seriously injured in Melbourne overnight, as police and paramedics warned drivers to be wary of revellers who may have been affected by alcohol in the lead-up to the New Year.

In the latest accident, a 35-year-old man was knocked unconscious and suffered serious head injuries when he was hit by a car near the corner of Punt and Bridge roads in Richmond just before 10pm.

The man's friend, aged 33, was also struck by the same vehicle and suffered cuts and bruising to his head.

Intensive care paramedic Alan Eade said paramedics arrived just minutes after the accident to find the 35-year-old lying unconscious on the road and having trouble breathing.

"They gently moved his head which opened up his airway and improved his breathing," Mr Eade said.