SCHENECTADY — The Woodlawn Preserve still sees its share of joyriders racing ATVs up the sand dunes, but it is no longer the sanctuary it once was to under-age drinkers and off-road racers.

This summer, for the first time, police patrolled the preserve regularly, using their own ATVs to chase down riders and charge them with trespassing. Dozens have been ticketed or had their ATVs towed in the past four months, and illicit usage has now decreased dramatically, police say.

Even visitors entering on foot were warned that they, too, could be arrested for walking through the ecologically sensitive pine bush area, although in June the Schenectady City Council voted to allow pedestrian traffic.

The community police officer for Woodlawn got in on the project as well, searching the woods on foot at night to track down teens racing their ATVs around bonfires during beer parties.

“A lot of the credit has to go to community police officer [Nicholas] Contompasis,” police department spokesman Christopher Wrubel said. “He’s kind of made it his personal mission. He tries to get up there every night. He’ll park his car and go in on foot.”

As the summer wore on, ATV riders tried to argue that they didn’t know the preserve was off-limits. Vandals repeatedly removed the preserve’s “no trespassing” signs, giving police no way to enforce the rule.

So officers simply towed their ATVs, leaving the riders to walk home and pay a towing fee before they could retrieve their vehicles.

“If they came in an area where we can’t find a sign, we can’t charge them with trespassing the first time we see them,” Wrubel said, before beginning to tick off the reasons why police could still tow the ATV. Reasons range from a lack of registration to unsafe use.

Contompasis has towed more than 20 ATVs and has warned at least another 20 riders in cases where he couldn’t find a reason to tow their vehicles. In one week alone, he towed five ATVs.

Eventually, Public Safety Commissioner Wayne Bennett said, riders got the message.

“The fact that the officers were up there more than ever before, word gets out,” Bennett said. “Prevention is just as effective as arrest. It keeps people from getting back there and destroying the terrain.”

The preserve is home to the largest sand dune in the Capital Region’s pine bush, but ATVs have severely damaged it, according to preservationists. Visitors have also thrown beer parties, complete with large bonfires, and have built trails for their ATV races, which have damaged wide swaths of the natural habitat, city officials say. The ATVs cause such damage that all motor vehicles are banned from entering the preserve.

Usually, police use their own motorized vehicles to catch the ATV riders. Two officers have received special training to drive small off-road motorcycles, similar to dirt bikes. Although the initial purpose for the bikes was to better patrol the preserve and other city parks, they have lately come in handy in a variety of other situations.

“We used them on the railroad tracks last week,” Bennett said. “We got a report of a guy with a gun. Obviously you can’t get a car down there. So we use them in a number of unorthodox patrols.”