a taxi meter runs on two elements ..distance travelled and time stationary, but never the two at the same time,
a one mile trip in heavy traffic will therefore cost more than it would in normal traffic,
a taxi drivers trick after seeing the lights change some distance ahead is instead of easing off and hope to arrive at the lights after they have changed to go, is to plough on full bore and slam on the brakes in order to gain a little 'waiting time',
if the driver is asked to wait he is entitled to request payment for the journey thus far and agree the approximate period of waiting required and accept payment in advance for that amount of time,
so if the area of operations has a rate of say �20 per hour waiting time and the customer wants the driver to wait for 30 minutes and the metered fair so far is �8.80 say then the driver should request �18.80 and on receipt is obliged to give the customer what he has paid for i.e. the extra 30 minutes wait,
all the time the meter will be tickingover so the driver should wait till his payment upfront is used up or the passenger returns to continue the journey,
there probably isnt a cabbie alive who hasnt been caught once by the 'can you wait for me guv' trick and sat there like a (unpaid) lemon for half an hour