Few people would think a public bus could turn into an inferno. Yet some 120 people found themselves trapped in a burning bus on Friday in Chengdu with their main routes of escape blocked and it appeared passengers could not find the safety equipment. The initial death toll of 25 is likely to rise; many of the survivors have been horribly burned. Our thoughts are with the victims and their families. But questions about how such a terrible accident could happen must be answered by an impartial investigation and anyone found negligent punished. At the moment, the incident appears to be an accident, though officials have not ruled out sabotage. The bus was clearly overcrowded. When fire broke out, passengers could not open windows or doors to make their escape. The bus driver and a lucky few squeezed through the side window by his seat. Witnesses said there were no safety hammers on board so they could not smash through windows. City officials yesterday claimed three hammers had been found; if so, they had probably been put in places not readily located by panicky passengers in an emergency. Fatal fires can happen anywhere, but negligence and dangerous habits can make them much worse. Most mainland cities now operate modern fleets of buses and other sophisticated means of public transport, but too many operators are not properly trained. A culture of safety is often lacking. While the driver in this case should be faulted for allowing so many passengers onto his crowded bus, it must be acknowledged that what he did is common among bus drivers in many mainland cities. Deaths on public transport or public premises can be minimised by safety features and a responsible work culture. These include the use of fireproof materials, installing firefighting equipment and making it accessible, and a ban on overloading. Awareness needs to be raised among operators - and passengers - to create a culture of safety. Above all, safety laws need to be adequately enforced; negligent or corrupt officials must be held accountable for their failings.