Increasingly traffic-choked Riyadh is planning to build a monorail mass transit system, the capital's governor said on Monday.

Routes, detailed designs and engineering for a 42-kilometre (26-mile) light monorail on two lines are ready and awaiting budget allocation, Prince Salman bin Adbul Aziz said in a report on infrastructure development.

"The planning commission has completed design and engineering specifications and implementation plans for the train and a comprehensive plan for bus transportation in preparation for launching the projects upon adoption of the necessary budget," said the report released by the state SPA news agency.

The metro will include a 25-kilometre (16-mile) roughly north-south line through the busy Batha shopping area in the heart of the old city and a 17-kilometre (10-mile) roughly east-west line in the newer north where a financial hub is under construction.

Salman also said a comprehensive network of buses was being planned in conjunction with the metro.

Earlier reports said the government was studying a mass transit system for the six-million-inhabitant capital but no details had been released.

With only a handful of mini-buses serving a few routes, Riyadh has virtually no public transportation, and commuters rely on company transport or private cars.

Salman's report gave no hint on how the city will deal with one of the overriding issues of public transport: how women, who are banned from driving and who are required to travel with a male guardian and avoid contact with unrelated men, will be able to make use of it.

Currently women must be driven to schools or jobs by a member of their family or a chauffeur, adding to the growing congestion on the city's streets.