New York City primary voters would be smart to double check their poll location before heading out to cast their ballots Tuesday.

Twenty percent of the city’s poll sites have changed since 2016, representing more than 200,000 eligible primary voters, according to an analysis by the WNYC Data News team of poll locations from the city's Board of Elections.

In some cases, people are in for big changes.

In Brooklyn's 43rd City Council district in Bay Ridge, voters from one election district that voted last November at PS 331 on Fourth Avenue will now vote at Fort Hamilton High School. The new poll location is a 30-minute walk from the old one.

In Manhattan's Chinatown, residents who used to cast ballots at PS 126 on Catherine Street will be split up, depending on their home addresses, between two new locations.

The reasons for the poll site changes vary, according to board officials. In some cases, sites were moved to meet accessibility requirements. In other cases, private buildings no longer wanted to host a poll site at their location. There are also some technical issues related to reapportionment that come into play under state election law in years ending with the number "7."

The city elections board mailed all registered voters information on their poll site the first week of August. If their polling place had changed, the mailer came with a conspicuous notice.

“There is a thick, red band on the front cover that says, ‘Alert, your poll site has changed,’ and that is meant to give attention to those folks so they double check their poll site information,” Michael Ryan, executive director of the New York City Board of Elections, told WNYC.

Poll site changes are not necessarily a bad thing — if they help elections run more efficiently.

“They just need to be implemented in a fashion where people know where they are going to vote,” said Chris Famighetti, a policy and research analyst at the Brennan Center for Justice. 

He also suggested that election administrators should follow some best practices to help voters people who end up in the wrong place — like posting signs directing people to the new polling site.

Here in New York City, board officials said they will only post signs if the location change was made after last month's mailing.

Voters can check their poll sites here.  And if you have any problems — let us know by tweeting @WNYC.

You can also contact the New York State Attorney General's office hotline at 1-800-771-7755 or email civil.rights@ag.ny.gov at any time Tuesday between 6 a.m. and 9 p.m.