To walk, or not to walk - that is the latest question for people using escalators. Commuters are now told not to walk along a moving escalator, instead of standing on the right and leave the other side open for those in a hurry to walk past. The safety campaign led by Mass Transit Railway is no doubt staged with good intention. But if it is to be seriously enforced, it amounts to overthrowing an unspoken but well received norm that has been serving the city well for decades.

Jostling for spaces along MTR escalators can be a thrilling experience. Yet commuters naturally split into a standing line and a moving stream once they step onto the escalator. The orderliness owes much to the unofficial rule adopted by many world cities. This is also reflected in the relatively low number of accidents. The MTR recorded 382 cases in the first seven months of this year, 12 per cent down from the same period last year. Less than half - 43 per cent - were due to people moving along escalators. It translates into fewer than one accident a day. With millions of people scurrying up and down the escalators throughout the city's rail network every day, the problem does not seem worrying.

Authorities in Japan have also started to promote standing still on moving escalators. Commuters are no longer advised to stand on one side to make way for others. They are also told to stand a step away from the person in front to reduce the danger in the event of an accident.