On a hot morning at the Tsim Sha Tsui bus terminus this week, the driver and passengers on the No5 bus were sweating profusely as the temperature reached 32 degrees Celsius - three degrees higher than outside.
Other buses in the queue were much cooler, because they had air conditioning, but this No5 bus was one of KMB's 260 non-air-conditioned buses, which were all supposed to be replaced this year.
'It is boiling hot, that's why we call it a 'hot dog' bus. The situation is even worse on rainy days when sweat, vapour and rain mix together,' said the driver, Lo Tak-keung, 46.
'Of course, I would prefer to drive an air-conditioned bus if I could,' said Mr Lo, who started driving buses four months ago and drives the 'hot dog' bus between Tsim Sha Tsui Pier and Choi Hung every day. 'But my seniors drove the older and even hotter buses in the past. I have to go through this because I am new.'
On the lower deck, a 70-year-old passenger who identified herself only as 'Madam Tsang' was fanning herself. 'I would rather choose to take the air-conditioned bus even it is more expensive. But when I am in a rush, I have no choice and take whatever bus comes first,' she said, adding, 'I feel like I am in a steam room.'
KMB began introducing air-conditioned buses in 1995 and pledged to phase out the old buses from its fleet of 4,021 buses by the end of this year. Yet the company has since postponed the full-replacement for three years, claiming some residents are reluctant to pay the higher fare for the new buses. The 260 old buses have raised concerns about air pollution and fare rises.
Polytechnic University vehicle emission expert Lo Kok-keung said the 'hot dog' buses were more polluting than the new buses. Vehicle emission is the main cause of air pollution at street level in Hong Kong.
'All the non-air-conditioned buses are pre-Euro [emission standard] models and manufactured before 1992, [so] the emission is roughly 20 per cent more than the new buses.' Mr Lo said. 'Besides, they [the 'hot dogs'] are less energy efficient because of the old design.'
Explaining the delay in the fleet's full replacement, a KMB spokesman said: 'We have faced opposition from some district councillors, saying the elderly in some areas find it difficult to accept the fare adjustment. Thus we postponed the progress and expect all buses will be air conditioned in 2010.'
Another concern was cost effectiveness.
'Other bus companies have about 1,000 buses each, but we have 4,000. We need to consider carefully when we buy new buses, based on the principle of cost effectiveness.' he said, adding that the average life span of a bus was about 17 years and that it took a while to replace them all.
Transport Department data shows KMB operates 99 out of its 400 routes with these old buses - mainly in run-down areas such as Sham Shui Po, Wong Tai Sin and Kowloon City. The difference in fare between air-conditioned and non-air-conditioned buses is 37 per cent on average.
KMB has pledged to phase out old buses by 2010
The number of buses on its fleet 4,021
The number that do not have air-conditioning 260