Sign language: A purist vents his anger at the sloppy use of language on TV, tubes and taxis ...

There is one moment on the television news that always infuriates me and I have finally realised why. It's just before the newsreader gives the score of the football match that is about to be screened and tells the viewer: "If you don't want to know the result, then turn away from the screen." I haven't the remotest interest in the result, so why on earth should the newsreader be cajoling me to join the massed ranks of football hooligans who, at that very moment, will be coyly averting their communal gaze from the television? So despite my passionate lack of interest, I keep my eyes rooted to the screen.

The true cause of my annoyance, however, is not so much my anti-football fanaticism as a purist's resentment at sloppy use of language. When he says: "If you don't want to know the result ..." he doesn't mean that at all. What he really means is: "If you want not to know the result ...". Only someone with a positive desire not to know the information on the screen should be instructed to turn away, not those of us who merely lack the desire to look at it.

London Underground falls into a similar loose language in its two escalatorial imperatives: "Please stand on the right" and "Dogs must be carried on the escalator". The first of these should simply be amended to "Please do not stand on the left", but the second poses more significant problems.

Taken at face value, it appears to deny access to the escalator to anyone not carrying a dog. This may, of course, have been the original intention. Perhaps in the early days of the Underground, passengers carried dogs down into the tunnels as an essential safety measure rather like canaries down mine-shafts. There was probably a cage full of dogs at the top of the escalators and an attendant passing one to each commuter. If the dog passed out at the foot of the escalator, the passenger would hurtle up the up escalator for a whiff of smelling salts. ("Had a terrible journey to work today, chaps. Got saddled with a Rottweiler on the Bakerloo.") Or they may have been sniffer dogs, trained to detect asbestos. What with staff cuts and improved ventilation, however, the practice died out, but the "dogs must be carried" signs remain.

Or it may be just another case of easily avoidable sloppiness. "Dogs on the escalator must be carried" would be a considerable improvement, though, it must be confessed, would not totally solve the problem for there is something unsatisfactory about using a passive verb in a call for action. The command is, after all, implicitly directed at the dogs' owners, though the opening words "dogs must" could hardly be better calculated to lose the interest of any non-canine. The ideal formulation would be: "Any person riding the escalator in the company of a dog or dogs is required to carry it or them respectively for the duration of his or her escalatorial sojourn." I strongly exhort London Underground to amend all their signs accordingly.

Until they do so, I would boycott the Underground were it not for the lack of linguistically pure alternatives. On buses, one is always liable to encounter a sign saying: "Do not stand forward of this notice." Quite apart from the perfectly horrid "forward of" (say "further forward than", dear, if you want people to think you're English), which side of the wretched thing is "forward"? Is it forwards, from the point of view of the person reading it, or from the point of view of the notice itself? The issue is further complicated by the positioning of such notices in a manner suggesting that the "forward" they refer to is actually one of the sideways directions, but how can one tell which sideways is forwards?

That leaves us with taxis, which would be all very well, but for their pseudo-polite "Thank you for not smoking" signs. Logically, such a message ought to, indeed must, be ignored by anyone who is smoking, yet such people are precisely those at whom the message is aimed. It's the same idiotic semiotics as interrupting a taxi-driver in mid-rant with the words: "Thank you for not talking to me." Anyway, thank you for not giving up before the end, and if you weren't interested, I hope you looked away.