Prepare for the slowest traffic of the year in Manhattan. The UN is in town.

And you thought the traffic was already bad.

The New York City Department of Transportation said drivers in Midtown can expect the slowest traffic of the year as the United Nations General Assembly takes place in the city this week – and this is just the beginning of a season of “congestion alert” days.

Average vehicle speeds will drop below 4 mph during the General Assembly (normally, traffic speeds are anywhere between 4 and 6 mph), the Department of Transportation said in an alert that asked New Yorkers to use public transit instead. Every weekday through Friday, Sept. 27, was designated as one of the city's 20 upcoming traffic congestion days in 2024.

The transit authority plans to provide a temporary bike lane for cyclists and small vehicle users in a portion of Midtown. Work is ongoing to make the design permanent.

According to an NYPD warning, the following streets will be closed during the General Assembly:

• First Avenue from 34th to 51st Street
• 42nd Street between First and Second Avenue, daily until 7:00 p.m.
• 44th, 46th and 48th Streets between First and Second Avenues

A more detailed list of roads affected by the General Assembly and other events is available from the Ministry of Transport.

According to a report released Friday by traffic expert Sam Schwartz – a former city transportation commissioner who coined the term “gridlock” – and state Sen. Brad Hoylman-Sigal, whose district includes much of Manhattan's West Side, average speeds in Midtown are at their lowest levels since records began. The report found that speeds were about 20 percent higher a decade ago, significantly slowing response times for emergency vehicles, police and firefighters.

(Schwartz is a proponent of the congestion toll plan that Governor Kathy Hochul put on hold indefinitely earlier this year, which was not initially implemented but may be reinstated at some point.)

No improvement is expected during the holiday season. The Ministry of Transport expects traffic jams on November 20-22 and 26, as well as on December 4-6, 10-13 and 17-19.