Fifteen people were arrested yesterday aboard a raunchy rolling radio-promotion bus after its topless female passengers drew crowds and stalled traffic, cops said.

The bus, which was promoting radio bad boys Opie and Anthony, veered on to a Midtown street cleared for a presidential motorcade. But that wasn’t the reason given for the arrests.

“It was creating a crowd condition,” a police source said. “They were flashing everybody.”

The crowds were encouraged by Opie and Anthony, who urged their listeners on WNEW-FM to have a look at the Greyhound-style bus as it rolled through Manhattan.

Stand-up comics Lewis Black, a regular on “The Daily Show,” and Jim Norton were among those busted. Also arrested were six models and two Opie and Anthony staffers.

Police said passengers on the “voyeur bus” would probably get desk-appearance tickets for minor offenses. But more serious charges were possible, officials said.

The bus features nude or semi-nude models in its giant picture windows. Fans can follow its nationwide travels on a paid Web site.