PROVIDENCE — A new study of the state police says troopers are stopping and searching cars driven by blacks and Hispanics more often than those driven by whites.

The study, commissioned by the former superintendent of the state police and conducted by faculty members at the University of Rhode Island, produced findings like those in two similar, statewide studies during the last seven years.

They say they found a pattern of “racial and/or ethnic differences” among motor vehicle stops and searches by the state police.

The results are consistent with what one would expect from biased law-enforcement tactics and amount to “a red flag” calling for more action, the study says.

While the study does not prove bias on the part of the troopers, the authors say, the discrepancies couldn’t be explained by other factors. The two earlier studies, by researchers from Northeastern University, ended in 2003 and 2006 and covered all police in the state. Based on records of hundreds of thousands of traffic stops collected by the police, they reported that most departments, including the state police, were stopping and searching cars driven by blacks and Hispanics more often than those driven by whites.

Unlike the two previous statewide studies, which were mandated by the General Assembly, this one was voluntary, commissioned by former state police Col. Steven M. Pare. Pare, who retired in February 2007, had said in interviews that he was troubled by the results of the previous studies and wanted to get to the bottom of the issue. He took some internal measures, including discussions with individual troopers.

His successor, Col. Brendan Doherty, however, largely rejects the URI study. He said in an interview that its findings in one key area –– who gets stopped –– are the product of a flawed methodology, and that the racial and ethnic differences it found in the other ––who gets searched –– don’t show a significant problem.

His troopers, he said, do not discriminate, and he would not tolerate it if they did. He said they receive substantial training aimed at the issues the studies have raised.

“It merits further study,” Doherty said, “but that doesn’t mean there’s a problem.”

He said he opposes anti-profiling legislation now before the General Assembly. The bills would require police to state the legal basis for searches in writing and would limit their investigations following traffic stops unless they could show a reason to believe criminal activity was involved.

Along with criticizing the URI study’s methods, Doherty pointed to the tiny number of complaints he said the state police have received from drivers — just five last year.

“If there was a problem, I would think we would have more” complaints, he said.

Like the two previous studies, the new findings are consistent with years of complaints by nonwhites that they are targeted by the police because of their skin color. Those complaints fostered the bitter joke that they were being pulled over for “driving while black.”

Civil-rights advocates say the new results add to a large amount of existing evidence that the police in Rhode Island discriminate against people of color on the highway, and that something needs to be done about it.

Steven Brown, executive director of the Rhode Island Affiliate of the American Civil Liberties Union, said in a letter to legislators that police departments still haven’t addressed the problems turned up years ago by the earlier studies.

The results of the state police study, he said, show that “strong and comprehensive racial profiling legislation” is needed, not more research.

The state police study was done by Leo Carroll, a professor in the URI department of sociology and anthropology, and Liliana Gonzalez, an associate professor in URI’s department of computer science and statistics, assisted by Hakmook Kang, a doctoral student and research assistant in Brown University’s biostatistics program.

In the earlier studies, officers had filled out data cards for each traffic stop; this time, troopers entered the information on laptop computers in their vehicles.

The authors analyzed data gathered by troopers during 2006 on 51,773 traffic stops, including 619 cases in which troopers had a choice about whether to search drivers, passengers or their vehicles, and did so.

The authors say they looked hardest at violations in which the police have the most discretion on enforcement, such as equipment and registration infractions and cases where pursuing a search is up to the trooper, because bias would be most likely to show up in those situations.

“There continues to be racial and ethnic disparity” in the drivers the state police stop, the study says. “This disparity occurs on all types of roads and in most, though not all, cities and towns.”

The difference in treatment is “only slightly less” on Route 95 than in the previous studies, it says.

The percentage of minority group members among those stopped on Route 95 fell from 27.6 percent in 2001-2003 to 24.8 percent in 2006, the URI study found, but it still remained higher than the estimated proportion of minorities on the road, 15.1 percent.

In vehicle searches, the authors say, there is “substantial evidence of racial and ethnic disparity” in searches where troopers have discretion in whether to search, and they found little change from the previous studies.

Doherty denied that his troopers are racially biased –– and Carroll and Gonzalez said repeatedly that they aren’t making that accusation.

In fact, the URI authors say at one point that they couldn’t be sure whether troopers used race as a basis for stopping vehicles without knowing what the officers were thinking at the time.

Instead, like the Northeastern researchers, they looked for unequal rates of enforcement and then used a variety of statistical tools to identify which factors caused the racial and ethnic differences.

They say some of their findings are what one would expect to see if racial bias were involved.

For example, they say that their traffic-stop findings “are consistent with what one would expect” if troopers “made use of racially-based pretext stops.” That refers to the police tactic of using a minor violation, such as a burned-out taillight, as a pretext for pulling a driver over in the hope of developing the legal justification to search his car.

The results also support complaints by nonwhites that they are stopped for no reason other than race when they drive through white areas.

The study says that the greatest disparity in searches occurred when black drivers were stopped in areas where few blacks live, while they were stopped as often as whites in minority neighborhoods. The authors say that suggests that black drivers were stopped and their vehicles searched because they seemed to be “out of place” in the white neighborhoods.

The authors say that might not reflect prejudice, but rather “police training and experience” because officers are trained to be suspicious of the unusual. But they said troopers must be told that the fact that a driver stopped for speeding in a rural part of the state is black doesn’t justify searching his car.

The authors conclude that if two drivers, one white and the other black, were driving vehicles of the same age, with no passengers, on similar roads in the same area at the same time of day, the black driver would be 1 1/2 times as likely to be pulled over as the white driver by troopers from the same state police barracks. Hispanic drivers would be slightly more likely to be stopped. “A driver’s race and ethnicity clearly influences the reason for which he or she is stopped,” even after a number of other factors are taken into account, the authors conclude. However, Doherty and Inspector Stephen Bannon dismissed the results concerning stops, saying the research was “inherently flawed.”

“I disagree with that whole part of the report,” Bannon said.

Doherty and Bannon focused on a difficulty researchers must address when they study traffic stops — the need for a “benchmark,” or estimate of the racial breakdown of drivers on the road during the study. That’s needed to compare with the proportions of the whites, blacks, Hispanics and other groups who were stopped.

Partly because the URI researchers refer to the benchmark “problem” in discussing their methodology, Doherty and Bannon said, the conclusions are suspect.

The URI authors say they relied primarily on benchmarks the Northeastern researchers developed.For Route 95, the Northeastern group had said, they repeatedly drove the highway from the Massachusetts border to the Connecticut border on weekdays and weekends, counting thousands of white and nonwhite drivers during 18 months ending in 2003. That’s a widely used approach in the now well-established field of racial profiling research.

For cities and towns, Northeastern created a model based on travel statistics, employment, retail trade, car ownership and other data to estimate the racial and ethnic breakdown of drivers. After police departments challenged those estimates in their first report, published in 2003, the Northeastern group said, they proved their accuracy by watching traffic in six communities and comparing the results with their estimates. Their “driving population estimate” technique, novel at the time, is now recognized in the growing academic racial profiling literature.

Searches are less complicated to analyze than stops because there’s no benchmark problem –– the racial makeup of the drivers stopped doesn’t have to be estimated because it’s already in the data.

The study found “substantial evidence of racial and ethnic disparity” in searches where troopers had discretion in whether to search, and said there was little change from the previous studies. Blacks were twice as likely to be searched as whites, and Hispanics 1½ times as likely. After adjusting for a number of factors that could explain some of the difference, the authors said, Hispanic drivers were no more likely to be searched, but blacks were still 1½ times as likely to be searched as whites.

However, despite the more-frequent searches, no more contraband (mostly drugs) was found among nonwhites than among whites.

The fact that troopers searched black drivers more often than whites but found no more contraband, the study says, suggests that there was less legal basis for searching the blacks. In fact, the state police found drugs and other contraband slightly more often in the vehicles driven by whites as in those driven by minorities. (Contraband was found in vehicles driven by: whites, 42.9 percent; blacks, 42.2 percent, and Hispanics, 40.5 percent.)

That is a major sore point among critics of the police. They ask what, other than race, would prompt additional searches of vehicles driven by nonwhites when police officers’ own experience shows that there are at least as many drugs and other contraband in whites’ vehicles.

Doherty acknowledged that “there’s a discrepancy there” in the search figures. However, he said, “I wouldn’t characterize it as a significant difference.”

Also, Doherty said, “Just because there was a difference, it does not mean it was unjustified.” He and Bannon insisted that the state police don’t discriminate.

“It’s totally unacceptable in our culture,” Bannon said. “We police each other. It’s not tolerated.”

blandis@projo.com