Why a taxi meter has two ways to count
A taxi meter is built to charge for two different things: how far the car carries you and how long the ride uses the taxi. On an open road, distance is the useful measure. In a jam, the car may cover almost no ground while the driver and vehicle remain committed to that trip, so the meter counts elapsed time instead.
The changeover is usually tied to a speed threshold programmed into the meter. Above it, distance-based increments accumulate; below it, time-based increments do. That means creeping traffic can count partly as distance and partly as time, rather than waiting for the car to become completely motionless. The exact threshold and fare rules vary by location.
The tradeoff behind the fare
Without a time component, a short trip through a long traffic jam could cost nearly the same as a quick trip over the same route. The meter would ignore the extra time the taxi could not spend on another passenger. Time charging accounts for that delay, though it also means the fare can rise even when the car barely moves.
This is why the route alone cannot predict the final price: the same streets can produce different fares at different times of day. A red light or a queue at a busy intersection is not a separate fee; it is the meter shifting from measuring ground covered to measuring the taxi’s time in use.
