At 7.58PM on Saturday, 30 April police were called to reports of a collision involving a car and a motorcycle in Court Road, Orpington.
Officers attended with London Ambulance Service paramedics and the London Air Ambulance.
The motorcyclist – an 18-year-old man – was taken to a south London hospital where he remains in a serious condition.
At 23:54hrs, officers attended a nearby address where they arrested a 50-year-old woman on suspicion of failing to stop at the scene of a collision and failing to provide a specimen of breath for analysis.
An investigation is under way, led by the Serious Collision Investigations Unit.
They are appealing for anyone who witnessed the incident and who has not yet spoken to police, or anyone who has relevant dash cam footage, to call 0208 285 1574, providing the reference 6500/30APR.