Intoxicated Driving Resource Center (IDRC) in New Jersey
If you are convicted of Driving While Intoxicated (or Driving Under the Influence) in New Jersey, you will be required to attend from 12 to 48 hours in an Intoxicated Driving Resource Center. These Centers are located in every county in New Jersey, but for the 48 hour program, there are only three locations (North, Central, and South). There are fees associated with attendance of these programs, which are separate from the fines and costs paid directly to the Court.
Even if you have attended before, if you are a second or third offender, you will be required to attend again. If you do not attend the IDRC as required, you will not be able to have your privilege to drive restored and you will be summoned to appear in court for "non-compliance". A judge can sentence you to spend this time in jail, but you would still have to attend in order to have your driver's license restored. It is important that you attend the IDRC when given notice to do so, as that will prevent more difficult problems later.
The State of New Jersey has also provided additional information on the Department of Human Services Website, and you can find a specific factsheet which may answer additional questions you might have.