The phrase "a flat fare" is correct and usable in written English.
It is typically used in the context of transportation, referring to a fixed price for a ride, regardless of distance or time.
Example: "The taxi service offers a flat fare to the airport, making it easier for passengers to budget their travel expenses."
Alternatives: "fixed rate" or "set price".
A flat fare of €30 covers most of central Madrid.
A flat fare's a flat fare (and I want to prove how savvy I am).
The increase is the first since 1995, and puts the cost of a flat fare at the upper end of urban transit systems around the country.
The cabs would travel in a designated corridor and charge passengers a flat fare to be dropped off anywhere along that route.
On transport, Berry has announced an ambitious plan to phase out fare zones and introduce a flat fare system within ten years.
What the prospective passenger needs to know from the outside is that the fare is metered — in other words, make sure the meter is on once you climb in, unless you're going to Kennedy International Airport, in which case it would be a flat fare.
He cited a one-year pilot of a taxi share program that was intended to allow passengers to pay a discounted flat fare along specific routes.
If she becomes Mayor, Jowell intends to freeze fares, introduce a flat Tube fare of £2.30 everywhere on weekends, and introduce one hour bus tickets, which will allow passengers to pay for one ticket that they can use on any bus for an hour.
When he took over as CCTV's premier ad salesman, he promised a radical departure from the flat fare long seen on state TV.
The flat fare will be $3 or $4 a head, significantly less than the regular metered rates, and riders can ask to be dropped off at most points along the route.
His manifesto also includes plans to set a flat bus fare rate of £1.50 and to freeze council tax for a third year.
