Q: I’m confused. The New York Civil Liberties Union, in its lawsuit, is criticizing searches on the subway because the searches are random and therefore ineffective. Would they prefer police stop only those who seem “suspicious”? Wouldn’t that lead to some kind of profiling? I can’t imagine the NYCLU would advocate that.

A: Indeed, the civil liberties union, in a lawsuit filed yesterday in a Manhattan court on behalf of five subway riders, called the police’s policy of random bag inspection “virtually certain neither to catch any person trying to carry explosives into the subway system nor deter such an effort.” The suit also alleges that the policy violates the Fourth Amendment, which states that searches must be conducted with reasonable belief of wrongdoing. The civil liberties union’s associate legal director, Christopher Dunn, told reporters that police would be better off narrowing the focus of their searches on “suspicious” people.

“You target people who you suspect of wrongdoing,” Mr. Dunn said.

The comment immediately sparked strong questioning from reporters, who asked whether Mr. Dunn’s suggestion would mean police should employ discretionary methods, not random ones, to determine whether to search an individual. It sounded as though Mr. Dunn and the NYCLU were heading down a slippery slope toward profiling — a notion the group’s executive director, Donna Lieberman, emphatically rejected.

“There is a world of difference between targeting people based on their ethnicity or race and targeting people based on suspicious behavior, and the Police Department of New York knows how to do it and that’s what they should be doing,” she said. How to define “suspicious behavior” was a question the civil liberties union left for the police to answer.

The crux of the Fourth Amendment, some authorities have said, is the word “unreasonable.” For a search to be legal, it must be a reasonable one. It would appear that the public believes the searches are, by and large, reasonable, since, of the subway system’s 4.8 million daily riders, only a handful — the NYCLU’s Mr. Dunn said “scores” of people — are known to have complained of the searches.

A group sympathetic to the NYCLU’s case has said 2,500 people have signed an online petition protesting the searches, at www.nosubwaysearches.org.

Other lawyers point to precedents that favor the police.

“We’re breaking new ground in this case,” an associate dean of Columbia University’s law school who specializes in criminal law, Debra Livingston, said. “We don’t have a case that’s exactly like this, but we have had cases where the court has upheld random stops to address concerns less weighty than the ones in this case.We also know from the court that different Fourth Amendment standards apply in particularly vulnerable locations like airports. Both these lines of precedent are very helpful to the city’s case.”

Q: What is that floating pontoon in the East River off the FDR Drive near the Queensboro Bridge?

The pontoons of which you speak are the “fendering system,” constructed to protect the temporary roadway of the FDR from wayward boats on the East River while the main portions of East Drive are rebuilt. The fenders consists of 13 “dolphins,” structures that in this instance are each 18 by 20 by 20 feet, which are anchored to the bedrock at the bottom of the river with 2-foot-thick chains whose links weigh 9 tons each. Connected to the dolphins is a 250-foot-long, 10-foot-diameter pipe with bracing inside. It took six divers to put the protective system together. The fenders were installed to protect the half-mile temporary roadway, which has been cantilevered over the East River since May 2004.

Please send your transit questions to transit@nysun.com.