Desk research against primary sources, with the issuing authority linked where a page states an official fee, rule or deadline.
The flag fall itself already tells you something about the trip’s likely cost profile — AED 5 from a standard pickup versus AED 12 starting from DXB reflects the airport surcharge built into the fare from the moment the meter starts, not a different per-kilometre rate once you are moving. Both figures assume the meter is actually running, which is the entire point of an RTA-licensed taxi over any alternative.
An unmarked car offering a ride outside the app or meter system is not a cheaper version of a taxi, it is an unlicensed one, which means there is no fare regulation, no meter reading of roughly AED 1.96/km to fall back on, and no operator to complain to if something goes wrong. Sticking to a metered RTA taxi or an app with upfront pricing removes that risk entirely rather than just making it statistically less likely.