Police are appealing for witnesses following a head-on collision at Coolaroo today.
Police have been told a black Mitsubishi Lancer with NSW registration plates was travelling north along Pascoe Vale Road just after 12.30pm.
It is believed the Lancer lost control and veered across a median strip before colliding head-on with a silver Ford Laser station wagon near Shankland Boulevard.
The driver of the Ford, a Meadow Heights woman aged in her 50s was taken to hospital with serious injuries.
The driver of the Mitsubishi Lancer, a 20-year-old Roxburgh man was arrested and is currently in custody assisting police with their enquiries.
Fawkner Highway Patrol officers are investigating and are keen to speak to any witnesses or anyone that may have seen the black Mitsubishi Lancer driving erratically prior to the collision.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au