Bus routes in Fremantle, Joondalup, Rockingham and Perth city centre are expected to be disrupted from 6am until 10am this morning due to industrial action by TWU members over wages and job security.

Transport Minister Rita Saffioti said the new Purple CAT would add an extra 470,000km on to the bus network, taking in parts of West Perth, Subiaco, Shenton Park, Nedlands and Crawley.

Transperth’s free high-frequency CAT buses are paid for with a city-wide parking levy and are among the most successful and well-regarded bus services on Transperth's metro network.