Drivers who have one for the road at Halloween parties may end up with court dates and unpleasant personal consequences.

Ninety law enforcement officers -- about twice the usual complement -- will stage the largest driving-under-the-influence checkpoint ever in Western Pennsylvania sometime between Friday and Nov. 3 on "a major highway in Allegheny County."

It will be set up on just one night at a single, undisclosed location, and will be dedicated to the memory of state police Cpl. Joseph R. Pokorny, who was shot and killed Dec. 12, 2005, while on duty on the Parkway West.

During the same period, as part of national Impairment Awareness Week, several local DUI task forces are planning smaller checkpoints in the region.

"We realize it's Halloween, but with the year-end holidays coming up, police want to send a message to the public that they'll be out there watching for impaired drivers," said Cathy Tress of the Pennsylvania Driving Under the Influence Association.

"Driving in Pennsylvania is a privilege, not a right. Consequently, drivers have a responsibility to themselves, their passengers and other people who are sharing the road."

The region's largest DUI checkpoint will involve personnel from the state police's Washington Troop B headquarters and Pittsburgh barracks, where Cpl. Pokorny was stationed, and the West Hills, North Hills and Pittsburgh DUI task forces.

Ms. Tress said at least 20 police officers will be checking cars simultaneously, an indication that the checkpoint will be set up on a heavily traveled traffic artery.

Three registered nurses will be on hand to draw and test blood from drivers suspected of being impaired by drugs or alcohol. A driver with a blood alcohol level of 0.08 or higher is legally drunk.

Other workers at the checkpoint will conduct field sobriety tests, write up operator and mechanical violations, handle DUI paperwork and arrange towing.

"We don't want to delay motorists any more than possible," Ms. Tress said. "The best advice I can give is for people to choose a designated driver, or leave bars, clubs and parties some other way besides getting behind the wheel."

DUI arrests at checkpoints are made on the spot. Drivers who can arrange for somebody to pick them up can leave after being processed; each will receive a summons by mail to appear before a district judge.

Police have never been known to conduct a checkpoint on an interstate highway in the region. But Ms. Kress said there's no law against it, though safety has always been the overriding concern because of speed and traffic volumes.

"We can't reveal the location" of the upcoming checkpoint, she said, "because it would defeat our purpose. Some people who routinely ignore the law would just avoid it."

Funds for DUI checkpoints and other safety programs such as the recent "Smooth Operator" to fight aggressive driving come from the federal government and are channeled through the Pennsylvania Department of Transportation.