Massive traffic on the N4 highway towards Pretoria CBD. Photo: Sakhile Ndlazi/Pretoria News.

Pretoria - Parts of Pretoria are this morning chock-a-block, with traffic lights not working due to Njala sub-station experiencing an outage. 

Vehicles are lined up on the N4 as well as on other roads in the east of Pretoria and Centurion. Motorists were visibly frustrated as they tried to maneuver around the traffic gridlock. 

Technicians are attending to the problem, according to the City of Tshwane.

The municipality said there was a 132kV trip at the substation. Residents said it sounded like a "loud pop".

In an update at about 8.30am, the city said: "A switch in the Njala substation has burnt. Technicians are busy assessing damage. More information on restoration will be communicated soon."

Utilities MMC Abel Tau said the trip resulted in an outage in most suburbs in the east.

Areas affected by the outage include Mooikloof, Wapadrand, Waltloo, Mamelodi, Willows, Pumulani, Pyramid, Koedoespoort, Highlands, Lynnwood, Brooklyn, Villeria Wingate Park, Aries, Kloofsig, Lyttelton and De Hoewes.

Pretoria News