Police are searching for a driver who not only abandoned his car after a crash in Sydney’s south-west, but also his unconscious passenger.

The Mitsubishi Magna was travelling on the Hume Highway at Yagoona at about 1am when it crashed into the back of a parked car near Auburn Road.

Witnesses spotted the driver fleeing the scene on foot shortly afterwards and called Triple Zero.

When crews arrived, they found a 21-year-old man unconscious and trapped in the passenger seat.

He was taken to Liverpool Hospital, where he remains in a stable condition.

Police are now trying to identify and find the driver.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000

A separate hit and run at Riverwood has caused chaos for Sydney commuters.

A white Honda Accord hit and destroyed a train signal box at the intersection of Romilly Street and Broad Arrow Road at Riverwood.

A motor vehicle has crashed through our boundary fence at Riverwood and damaged some of our signalling equipment.
As a result, some #AirportLine services may experience some delays.
Crews are on site working hard to keep services running safely and on time. pic.twitter.com/8S7xyFpNSQ

— T8 Sydney Trains (@T8SydneyTrains) February 10, 2019

When police arrived at the scene at around 2am, the driver had fled the scene.

Buses are replacing some trains on the Airport line as crews work on the problem.

For updated service information, visit the Sydney Trains website.