One of the decoy speed cameras sits near Laurel Elementary School. City police hope their decoys will encourage drivers to follow the speed limit. (Matt Zapotosky/The Washington Post)

In the increasingly mechanized war on Washington area speeders, a new weapon has emerged.

Speed camera boxes — with sandbags inside.

Laurel police this week installed two of the off-white, waist-high cubes on Main Street downtown and on Montgomery Street in front of Laurel Elementary School, hoping their mere presence would slow down fast drivers. The idea is that those who have ever received a $40 ticket from one of the city’s six real speed cameras will see the “decoy” box and hit the brakes.

“It’s a crapshoot whether or not that’s got a camera in it,” Laurel Police Chief Richard McLaughlin said.

Yes, Laurel police are — bad pun alert — sandbagging would-be speeders. But their effort is not the first trick area police have pulled to encourage people to obey traffic laws.

Prince George’s County police keep up their “photo enforced” signs at sites where the actual speed cameras have been removed, said Maj. Robert Liberati, who is in charge of the county’s 72 speed cameras. And how about those signs that warn motorists that their speed will be “monitored by aircraft”?

“Nobody does that,” Liberati said. “Things like that set the tone.”

D.C., Prince George’s and Montgomery County police said none of their speed cameras are fakes. Bowie police said that although they rotate eight cameras among 14 boxes, all are “actual working sites,” in some sense. AAA spokesman John Townsend said the Laurel decoys, reported first by WRC (Channel 4), seem to be a “new frontier” in mechanized traffic enforcement.

“This is stealth technology,” he said with a laugh. “In basketball, you have the head fake. In football, you change the cadence of the signal from the quarterback. It’s all about faking, and it can be just as deadly and devastating.”

On Montgomery Street in front of Laurel Elementary, people had mixed reactions to the revelation that the box emblazoned with Laurel’s police logo was just that — a box. Dareyl Plue, a physical education teacher who watches the kids disembark from buses every morning, said drivers do speed down the residential road. But would a fake camera slow them down?

“If that doesn’t get out, it works,” he said, looking quizzically at a newspaper reporter asking him about it.

Police officials said real speed cameras have been effective in Laurel and elsewhere, although they acknowledge that they are sometimes controversial for the massive revenue they generate. Drivers grumble especially in the District, which raised $11.6 million from one speed camera on New York Avenue alone during a 23-month stretch ending in August.

Laurel, by comparison, netted $1.42 million in fiscal 2012. McLaughlin said he is not concerned with the cameras as a money-maker; after all, he paid $2,500 apiece for two boxes that earn nothing. The cameras, however, are effective in slowing speeders, McLaughlin said. In 2011, he said, police issued about 90,900 speed-camera tickets. In 2012, that number fell to about 39,600.

And even the decoy boxes — which are installed in areas where working cameras would be legal under state law and are identical to the real ones — seem to work. At both sites Thursday afternoon, several drivers hit their brakes as they noticed the boxes. To those who worried that they might not have done so in time, fear not. There is no ticket in the mail. But maybe next time slow down around a school, would you?