An elderly couple were rushed to hospital after being cut free from their overturned car.
Emergency services were called to Northway in Maghull at around 2.35pm to reports that two cars had been involved in a crash.
It is believed that a black Ford Fiesta landed on its side after colliding with a blue Ford Focus.
A man and a woman, both in their 70s were freed by firefighters who were forced to remove the roof of the car to get them out.
A spokesperson for the North West Ambulance Service said: "We attended the scene of a two vehicle crash with two ambulances, and rapid response vehicle and an advanced paramedic.
"Two people, a man and a woman were taken to hospital in serious condition."
Merseyside Police officers closed the road from Damfield Lane to Kenyons Lane which is causing severe traffic delays in the area.
A spokesperson for the force said: "A woman in her 70s was taken to hospital with a serious arm injury while a man, also in his 70s, was taken for treatment to a serious head injury.
"The driver of the other car stopped at the scene.
"Road closures are currently in place on the road while enquiries are carried out."
Travel site INRIX said: "A59 Northway in both directions closed, heavy traffic due to accident from Damfield Lane to Kenyons Lane.
"Congestion to routes through Maghull , traffic is especially heavy on Liverpool Road North.
"The road has been closed since around 16:20. affecting travel between Liverpool and Ormskirk."
