Pedestrian killed on Sydney motorway

A woman has died after being hit by a car on the Hume Motorway in Sydney's southwest with drivers being warned to expect traffic delays.

The pedestrian was hit at 3.10am on Wednesday near the Narellan Road on-ramp, with police closing one of two northbound lanes on the Hume Motorway for several hours.

The male driver has been taken to hospital for mandatory breath testing, a NSW police spokeswoman said.

All lanes on the highway reopened after 7am, but motorists in the area can expect delays.