It happened on the southbound carriageway just before 9.30pm on Tuesday, July 31.
If you can help, please call 101 quoting ISR 857 of July 31.
Officers investigating a collision on the A1 Barnet bypass are appealing for information and witnesses.
It happened just before 9.30pm on Tuesday, July 31 on the southbound carriageway, at the junction with Trotters Bottom.
A black RT 125 motorcycle was in collision with a grey Peugeot Boxer van, leaving the motorcyclist – a 19-year-old woman – with serious and potentially life-changing injuries. The driver of the van was not injured.
PC Kirk Caldicutt, from the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit, said: “We are keen to speak to anyone who may have witnessed what happened, or the events leading up to or following the collision. Any piece of information, however seemingly insignificant, could prove very helpful to our investigation.
“We would also like to speak to any drivers who were using that stretch of road around the time of the collision, and have dash cams fitted to their vehicles. If you do, please make contact with us.”
Alternatively, you can contact the independent crime-fighting charity Crimestoppers anonymously on 0800 555 111 or through their Anonymous Online Form. No personal details are taken, information cannot be traced or recorded and you will never need to go to court.