Uber's low-cost taxi service is facing stiff opposition in Washington, DC, thanks to new regulations that forbid some fuel-efficient cars from operating as sedans. The company launched its UberX service earlier this month in Washington and other cities, putting it in direct competition with lower-cost cabs. The service operates in essentially the same way as Uber's original app, albeit with midsize, hybrid cars rather than luxury sedans. On Monday, however, the District of Columbia Taxicab Commission (DCTC) determined that midsize cars such as the Toyota Prius are not eligible to operate as sedans, much to the disappointment of Uber.

Under the DCTC's regulations, sedans for hire will be limited to the "vast majority" of luxury class vehicles, as defined by the Environmental Protection Agency (EPA); these categories include "Luxury Sedan," "Upscale Sedan," and "Sport Utility Vehicle," but do not include the midsize hybrids in the UberX fleet.

"we do not plan to take this lying down."

Uber criticized the regulations in a blog post yesterday, saying they "grossly restrict competition and affordable consumer transportation options." The company also pointed to a June letter from the Federal Trade Commission (FTC), which urged DC regulators to ease restrictions on Uber and other taxi-calling apps, saying they could stifle competition.

The DCTC says the new regulations still allow for "more than 40" hybrid or alternative fuel cars, and that it would "not be appropriate to add in the Prius or other basic, economy cars." The commission added that services like Uber threaten to force some traditional taxis out of the market, leaving many residents without viable options.

"Visitors without smartphones could not use a street hail to obtain service and residents who do not use or cannot afford smartphones — including those in under-served areas of the city and the elderly — would be left with nothing," the report reads.

Despite these restrictions, Uber says it remains determined to gain a foothold in the DC market.

"While we’re still figuring out how to operate within this regulatory environment, rest assured that we do not plan to take this lying down," the company said. "We remain committed to doing everything we can to ensure that everyone in the District can enjoy affordable and efficient transportation options."