LEE Siu-kin has explained on behalf of the Commissioner of Police (South China Morning Post, April 20), that the rule about not being allowed to board taxis on the departures level at Kai Tak is enforced as a matter of safety and ''in order to avoid any confusion''. I expected this reply, although I am surprised that there was no explanation of the authority by which I was made to go back downstairs and join the overcrowded queue at arrivals. I was not ''requested'' to use the ground level queue, as Lee Siu-kin has stated, I was ordered to do so. On the night concerned, there was no question of safety as there were virtually no passengers alighting from taxis at departures. I was trying to ''avoid any confusion'' myself, as the taxi queue at arrivals was backed up to the terminal doors. How did sending me back downstairs help? At the time there was a stream of empty cabs passing through departures, most of whom were heading back to Kowloon, because there was no space for them in the jammed taxi arrivals lanes. I do not dispute the need for order or safety, but within those important constraints, such rules need to be applied with a degree of flexibility, ''to facilitate airport users'' as Lee Siu-kin has suggested, especially on holiday weekends when Kai Tak's strained facilities are pressed beyond their limits. IAN DUBIN Wan Chai