The MTR's reach, efficiency and high standards are such that many of us have come to depend on its services. Understandably, then, when something goes wrong, as happened on the Tseung Kwan O line on Monday, there is immediate frustration and anger. But the power failure that brought trains to a halt for almost five hours was, by the company's criteria and the expectations of Hong Kong people, no ordinary breakdown. The reason for the chaos that ensued has to be thoroughly investigated so that measures are put in place to prevent a repeat. Early findings point to a 30-metre section of overhead power cable between Yau Tong and Tiu Keng Leng stations having come loose. The power outage is suspected to have resulted from a train coming into contact with the cable, which had been checked the previous night by MTR contractors. An MTR Corp official said it expected of contractors the same standards it applied to itself. But there are any number of reasons behind such a failure and conclusions should not be drawn or fingers pointed until the MTR Corp's report is released. As with any major incident on the MTR network, a preliminary report has to be in government hands within three days. Such promptness is essential given the importance of the MTR to our city; it is one of the busiest rail systems in the world, carrying passengers who make 4.4 million trips a day. But its significance goes far beyond the numbers. Tseung Kwan O district, like many others in our city, is built around and heavily reliant on trains for transportation needs. It is because of that reliance that the 12.40pm outage threw commuter transport along the line and throughout the MTR network into disarray. Buses struggled to cope and streets in Tseung Kwan O were quickly choked. The shutting down of much of the rail line backed up traffic elsewhere on the network. Stations were flooded with confused passengers, many complaining about a lack of information. There has not been so serious a breakdown for a decade. The MTR's world-class reputation has been dented. Service disruptions are uncommon, but not rare; a fire on the Tseung Kwan O line's North Point platform in January caused three-hour delays. But accidents that cannot be foreseen also happen and that has to be taken into account whenever trains are delayed. If the latest incident was preventable, though, responsibility has to be quickly determined and fixes made.