VARIABLE speed limits will be enforced on a busy stretch of Kwinana Freeway as part of a $47 million plan to create Perth’s first “smart freeway”.

The concept is similar to “smart motorways” in the UK, such as the M25 circling London, which slash speed limits during busy times to manage congestion.

Camera Icon Where the 'smart freeway' speeds will be enforced. Credit: PerthNow, Main Roads WA

In the UK, the speed limit is displayed on overhead gantries which are also fitted with cameras to catch and fine speeding motorists.

A spokesman for Transport Minister Rita Saffioti confirmed variable speed limits on the 15km stretch of Kwinana Freeway would be legally enforceable.

However, he said fitting speed cameras to the 13 gantries along the route was “not within the current scope of the project”.

Upgrades to the freeway, between Roe Highway and the Narrows Bridge in Perth’s southern suburbs, will start in 2018-19. Changes include:

CONVERTING the emergency stopping lane between Canning Highway and the Narrows Bridge into an extra lane, providing capacity for up to 2000 extra vehicles an hour.

DETECTORS in the road to determine how busy the freeway is and to provide information to the Control Centre.

ELECTRONIC signs to display which lanes are open or closed for an accident or to allow emergency services through.

CO-ORDINATED ramp signals to balance traffic flow coming onto the freeway, making merging easier and and reducing stop-start conditions.

RAMP signals are planned at Farrington Road, South Street, Leach highway (two ramps) and Cranford Avenue.

“This project is a first for Perth and provides an innovative answer to Perth’s freeway congestion,” Transport Minister Rita Saffioti said.