At all times, left turns are banned, except for Metropolitan Transportation Authority buses at certain locations.

[Read more about the new restrictions.]

The goal

The rules are part of a series of measures that city officials hope will lessen New Yorkers’ dependence on cars, which clog streets and pollute the air.

The restrictions, which are also aimed at making it easier for M.T.A. buses to traverse 14th Street, are part of an 18-month pilot program that could be made permanent.

The precedent

Restricting cars on a crucial city street may seem shocking, but it’s not unheard-of.

My colleague Winnie Hu said the partial ban was modeled after an effort in Toronto, where cars are banned from a 1.6-mile stretch of King Street, which like 14th Street is an east-west thoroughfare. The restriction has made streetcar service more speedy and reliable, she said.

Paris bans cars from its city center one Sunday a month. In Barcelona, cars are pushed to the outskirts to turn some intersections into playgrounds. Drivers in London must pay a congestion fare to enter the busiest parts of the city (a tactic New York will put in place in 2021).

The reaction

Those who support the new restrictions in New York say the change could drastically speed up bus service along 14th Street, which crawls at an average of just 4.5 miles per hour.

“New York City is failing bus riders on a daily basis and we are hemorrhaging riders as a result,” said Corey Johnson, the City Council speaker, whose district includes 14th Street.