Police in a growing number of U.S. cities are trying to silence the roar of dirt bikes and all-terrain vehicles on their streets this summer.
Packs of illegal riders who flout traffic laws while doing wheelies and other tricks on city streets are "an enormously challenging problem for us," Baltimore police spokesman Anthony Guglielmi said.
Last week, Baltimore police seized 15 dirt bikes and ATVs from a self-storage facility, including six that had been stolen and three with obliterated serial numbers.
Philadelphia police have made several sweeps in the past year to confiscate more than four dozen unlicensed dirt bikes and ATVs.
The crackdowns come as crashes have injured or killed some riders.
In New York City, a Bronx man died this month when a police car rear-ended his dirt bike, according to news reports.
The collision happened in a neighborhood where residents had recently complained about packs of young riders speeding through streets.
Many residents say they welcome the police effort because the illegal riders pose a safety hazard to pedestrians and other motorists.
"It's pretty common to see people going up the wrong way on a one-way street, going through stop signs, riding up on the sidewalks," said Dee Watson, 31, of Wilmington, Del.
A rider in Wilmington suffered serious head injuries Thursday evening when his Kawasaki dirt bike collided with a station wagon at a city intersection. The vehicle's driver suffered minor injuries.
Brenda Hamilton, 42, of Wilmington, works behind the counter at the 7th Street Deli & Grocery near the crash site and heard the collision, just after hearing the bike speed past the store and through a stop sign.
"It was chilling," Hamilton said.
Wilmington police say dirt bikes and ATVs aren't a rampant problem in the city. But residents say they are common, especially on warm summer evenings.
"People do it to see if they can get away with it," said Courtney Pruden, 24, of Wilmington.
"It's an adrenaline rush to see if they can get from one place to another without getting caught," she said.
Baltimore uses its network of nearly 600 surveillance cameras and its helicopter unit to track the illegal riders, waiting for them to stop before trying to arrest them, Guglielmi said.
In May, officials in Bridgeport, Conn., announced a crackdown on illegal all-terrain vehicles in the city and at Veterans Memorial Park, where they said riders were frightening visitors and disturbing the peace.