Motorists in Nairobi county will be fined a maximum of Sh25,000 if they defy the new 50kph speed limit set for vehicles bound for the CBD.

Speeds are being monitored following the installation of new cameras, the NTSA said, in a notice that indicated the starting points of the speed restriction.

It will start at City Cabanas on Mombasa Road, the KWS gate on Lang'ata Road, Nakumatt Junction ong Ngong' Road and from Nakumatt Junction to the Uthiru turn-off on Naivasha Road.

The limit begins at the junction of James Gichuru Road along Waiyaki Way, at Mobil Petrol Station on Peponi Road and the Muthaiga Mini Market on Limuru Road.

On the Northern by-pass, the application of the rule starts at the Nyayo Barracks roundabout, and from Ridgeways on Kimabu Road.

The authority said motorists plying Kangundo Road will stick to the speed limit from Kangundo Road, and from the Utalii Drift on Thika Road.

"All other roads in Nairobi that are not listed are considered to be within the limit," the authority said.

The Traffic Amendments Act of 2014 states that motorists will be fined Sh10,000 if driving by 5-10 kph above the new speed limit.

One will be fined Sh15,000 for driving between 11 and 20 kph past the limit, and Sh20,000 for exceeding it by 21-20 kph.

Any motorist who exceeds the limit by 31 kph or more will be fined Sh25,000.