BEIJING -- The Beijing metro authority has begun renovations of the city's old metro system for the purpose of improving convenience for passengers.

The Beijing Subway Co said that improvements of the old metro system will allow passengers never to lose signals on their mobile phones and shorten intervals between metro trains.

The building of barrier-free passages and establishment of traffic signs in braille and handrails at subway stations will greatly improve convenience for the disabled people, the company said.

Renovation work on No 1 and No 2 subway lines, which were built in the 1960s, is in full swing, and is expected to be completed next April. By then, wireless telecommunications networks will cover Beijing's all  subway lines.

New subway trains, which are wheelchairs accessible, will be introduced on the improved subway lines, said the company in its work progress report.

The company said that a total of 120 new trains will be added on the No 1 line, Beijing's east-west trunk line, to cut the intervals to two minutes and a half by the end of June next year. Another 144 new trains will be added on the No 2 line, an underground loop line paralleling the ground second ring road in downtown Beijing.

The new stainless steel trains have started trial running on a spare section of the city's rail route.

The Beijing Municipal government has spent nearly 4 billion yuan (US$526 million) to upgrade two metro lines prior to next summer's Olympics.

Currently, Beijing has four rail lines totaling 114 kilometers, carrying 2.1 million passengers a day. The city will have nine lines totaling 200 km by 2008, and 19 lines totaling 561.5 km by 2020.

Beijing's No 5 subway line, which runs through the heart of the city from north to south, opened to traffic last week.

Construction on the second phase of the No 10 line, the Yizhuang line and the No 8 line is scheduled to begin before the end of this year, according to plan.