Uber CEO Travis Kalanick. Barry Chin/Getty Images Four years ago, Uber started operating in New York City. At the time, it was a small company.

But today, New York is one of Uber's biggest markets, generating hundreds of millions of dollars in revenue annually. There are more Uber vehicles than taxis on New York City's streets.

On Wednesday, New York City's Taxi & Limousine Commission published a series of newly proposed rules for how for-hire vehicles like Uber can operate.

Among the TLC's proposals for companies like Uber is something that would prevent drivers from using Uber's turn-by-turn directions while they're driving a car.

From the proposal:

"Any smartphone application through which a Passenger can request FHV [for-hire vehicle] service must be available to a Driver ONLY when the Vehicle is standing or stopped, except that a smartphone application can permit a Driver to accept a dispatch with a single touch using pre-programmed buttons or using voice activation while the vehicle is in motion. All other use of the smartphone application must be velocity gated to prevent its use while the vehicle is in motion."

If this rule is approved, it seems like Uber drivers wouldn't be allowed to navigate on their phones while they drive. This proposed rule does not appear to affect drivers who have standard GPS systems in their cars.

NYC mayor Bill de Blasio is also behind an initiative that would require for-hire vehicle companies like Uber to get his approval before updating an app's user interface. Companies would also have to pay $1,000 every time they upgrade their user interface.

Facebook, Twitter, Google, and other tech companies and organizations wrote an open letter to de Blasio protesting the proposal. "We are troubled by the substance of the draft, which appears to indicate a significant departure from this administration’s policy of encouraging innovation, one that risks undermining New York’s progress and status as a global leader," the companies say in the letter.

NYC mayor Bill de Blasio. Twitter/@TechCrunch

Meera Joshi, who heads up the NYC Taxi & Limousine Commission, insists that de Blasio's regulatory plans would just “codify basic safety and consumer protection requirements that most apps have already adopted, and, to a large extent, it is their best practices that are the backbone of the rules," according to a statement obtained by the New York Times earlier this month.

In addition, Joshi says the administration won't personally review each app upgrade, but only ones that could impact drivers and passengers.

The tough stance on ride-hailing apps come as the de Blasio administration seeks to raise New York City's profile as a center for innovation. The city is pouring $80 million into the CUNY school system to grow its STEM educational programming. NYC's Tech Talent Pipeline, which trains New Yorkers to work in the NYC tech sector, is another government initiative that will cost $10 million. In addition, de Blasio has committed $70 million to equip all New Yorkers with broadband access by 2025.

Earlier this year, the New York City Taxi & Limousine Commission briefly suspended five of Uber's six New York City bases in January — an essentially toothless punishment handed down because Uber refused to give the TLC its ride data. New York politicians have been trying to get Uber to cap its controversial surge-pricing policy too.