Meanwhile, some app makers have said that the service has been slow to get started because the TLC's rules are cumbersome, especially a section intended to mollify concerns from vendors who provide the meter and credit-card systems to the 13, 000-strong fleet.
The structure of the charges can vary depending on payment method (by direct debit, pre-payment meter, or credit transfer such as cheque), on whether it is an internet-only tariff, which part of the country the customer lives in, if the deal involves a fixed price, when the deal was launched, how long it lasts, and so on.