Two road workers are in hospital in a serious condition after a crash on Great Eastern Highway near Graham Farmer Freeway just before midnight.

The two men in their 30s were injured when an oncoming SUV smashed into them, while they were standing by their stationary Mitsubishi Triton ute and trailer.

One of the workers was pinned between the two vehicles.

The SUV driver fled the scene and was located on Francisco Street.

Both men were taken to Royal Perth Hospital with serious leg injuries.

It took about six hours for emergency services to assess the scene and clear the crash site.

The driver of the car is in custody and assisting police with their investigations.

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