Farting in taxi cabs is a largely undiscussed and thus far wholly unresearched subject. Nevertheless, the phenomenon is real and can have unintended consequences. Suspicion may become mutual between cabbie and fare and still the matter is seldom, or never, raised. My own feeling is that there should be a tariff on all releases of hot air in confined spaces, howsoever expressed, though there are of course practical problems in the realisation of this ambition. A vexed question, to which there is no obvious answer. Winding down the windows sometimes helps.