Authorities say the New Orleans truck attacker placed two IEDs in the French Quarter. The photo shows rolls of nails and what appears to be a radio receiver inside a cooler.

During major events such as New Year’s or Mardi Gras, the source said, city security plans call for parking large vehicles at the ends of Bourbon Street that are most vulnerable to high-speed vehicle attacks. But such measures, the person said, are not practical on a daily basis in the crowded tourist zone.