I AM already resigned to being unable to persuade a taxi to stop for me during rain or a typhoon signal, but recently I have noticed taxi drivers becoming ever more discriminating in the passengers and/or destinations they will accept. Trying to get a visitor to the airport from Tsim Sha Tsui one evening at 10.15, I found no cabs coming to the Star Ferry rank, although plenty were patrolling Canton Road with their ''For Hire'' signs covered up. With his plane's impending departure my friend had to persuade a hotel doorman to flag one of these down and then negotiate a flat fare of $50. At 8 pm last Friday we would have been quicker walking to Lan Kwai Fong from Wan Chai. Only taxis with ''For Hire'' signs obscured were plying Lockhart Road. One picked us up but after 10 metres told us to get out after establishing our destination. Eventually a driver offered to take us for $40. On Sunday, I needed to take four bags to work. No cabs were cruising for hire and the one I telephoned for failed toshow. Finally one pulled up outside my apartment block to off-load a fare. With his ''For Hire'' sign illuminated I hailed him and he opened the door. He refused to take me to Kowloon saying he didn't know where Ho Man Tin was. Before I could bundle my bags in he drove off with the door open. Unless these bandits are forced to mend their ways, this city will become gridlocked and asphyxiated as people, in frustration and desperation, buy their own cars. G. M. PINCHES Happy Valley