SHANGHAI, Oct. 10 (Xinhua) -- Shanghai is speeding up urban rail construction, with total length expected to reach 800 km by 2020 from the current 617 km, transport authorities said Tuesday.

Shanghai has 15 urban railway transit lines currently in operation, and three more will open by the end of the year, Xie Feng, director of Shanghai municipal commission of transport, told a press conference.

Starting April 28 this year, six downtown lines have extended service hours beyond midnight on Friday and Saturday.

According to Xie, the public transportation network carries nearly 18 million passengers every day, with over 50 percent by urban rail transport.

The city is also developing "green" bus services, with new energy buses reaching 23 percent of the total. More electric buses will be introduced to realize "zero-emission" in the city proper, he said.