The MTR Corporation has spent HK$4 million to expand the trial use of environmentally friendly lights to three trains and a station, though a professor has said Hong Kong still lags the mainland in the use of such lighting. The high-brightness light-emitting-diode (HB LED) units use 30 per cent less electricity and have a lifespan that is three times longer than that of traditional fluorescent lighting, Jacob Kam Chak-pui, head of operations engineering at MTR Corp, said yesterday. 'The light colour of HB LED resembles natural lighting and serves better those reading books and newspapers when travelling on a train.' The company will consider increasing the number of trains using the lights to 100 after a two-year trial. One train with the HB LED lights started running on the Tsuen Wan line this week, and two others will get the new lights by June. Choi Hung station will be the first to be fitted with the HB LED lights. Work was expected to be completed by August. MTR Corp started the trial in 2006 when it installed HB LED lights in one train compartment. The lights cost 5 to 10 times more than traditional fluorescent lights, said Philip Chan Ching-ho, dean of Hong Kong University of Science and Technology's school of engineering. 'The mainland put LED technology into use two years earlier than Hong Kong,' he said, adding that the opening ceremony of the Beijing Olympics used the lights. LED lights will also be installed in 100,000 street lights around the mainland this year, Professor Chan said. 'Hong Kong is very slow [in adopting LED lights],' he said. 'The government should take the lead to do more environmentally friendly work.' Areas that are lit almost round the clock, such as shopping malls and the airport, could be good places to try LED lighting, he said. The Taiwan Taoyuan International Airport already uses the lights.