Isabelle Cadis, 55, failed to yield properly at a junction, blocking the roadway as the motorcycles approached at 50 mph.
Despite their efforts to evade the impending collision, both riders struck the vehicle at high speed, resulting in multiple fractures.
The incident occurred shortly before 11 am on June 8 last year on the B1108 Norwich Road at Carleton Forehoe, near Wymondham.
Cadis, residing on Holkham Road in Wells-next-the-Sea, entered a guilty plea at Norwich Magistrates’ Court for two counts of causing serious injury through careless driving.
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Prosecutor Stephen Munton stated that she executed an “unsafe manoeuvre” when her Ford Fiesta Zetec “failed to stop at the junction and subsequently obstructed the lane, leading to the collision.”
“These are serious offences considering the nature of the injuries and their repercussions,” he added.
The motorcycle rider was left unconscious with a broken pelvis, leg fractures, five broken ribs, and a fractured shoulder, while his passenger suffered a fractured cheekbone, a broken arm, and pelvic injuries.
The court heard they had approached the crossroads from the Kimberly direction when the car unexpectedly drove out from Barnham Broom Road, leaving them no chance to avoid crashing.
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The motorcycle rider informed police that the incident occurred even though he had slowed down and exercised caution at the wooded section of the road leading to the junction.
The road was closed for several hours to enable emergency services, including ambulance and fire crews, to respond to the scene.
Magistrates imposed a provisional driving ban and postponed sentencing until March 20, requesting a comprehensive pre-sentence report.
The court noted that the starting point for sentencing could range from 12 months of imprisonment to a high-level community order.