Pittsburghers have been watching digital billboards flash messages along the city's major routes for a while now but the region's challenging topography scared away researchers trying to weigh in on the debate over whether or not the electronic signs are a hazard to drivers.

Still, since the resulting research isn't likely to end the argument, maybe it's just as well to be on the berm for this one.

A nonprofit group administered by the Outdoor Advertising Association of America said last week that two new studies indicated digital billboards seem to attract more attention than the old-fashioned kind but found no correlation between the glowing signs and more accidents.

An anti-billboard group immediately blasted the studies as flawed, incomplete and self-serving. "No one has proven that these signs are safe yet," said Kevin Fry of Scenic America, a beautification organization based in Washington, D.C.

The ongoing discussion over the impact of the electronic billboards is heating up as the lighted versions slowly replace traditional ones. About 500 of an estimated 450,000 billboards in the United States use digital technology, according to the Outdoor Advertising Association of America.

Communities around the country, including some in Western Pennsylvania, have wrestled with the implications and attempted to put rules in place to make the signs as safe as possible. The Federal Highway Administration has indicated it sees a need for more research.

In the meantime, the Foundation for Outdoor Advertising Research and Education commissioned the two studies just released.

The first, done by researchers at Virginia Tech's Transportation Institute, involved having 36 drivers follow a 50-mile route around the Cleveland area in a vehicle equipped to track their speed, lane movements and film their eye movement. The test drives took place in late 2005 and early 2006.

Researchers initially considered doing the study in Pittsburgh, another city that had enough digital billboards in place to help in the information gathering. But a check of the proposed route pretty quickly ruled out the Steel City.

"The Pittsburgh streets where the digital billboards were located were generally very curvy and hilly, often with nearby intersections," according to the study's description of the methodology.

The route would have required numerous turns and made any kind of speed analysis difficult, said researcher Suzanne E. Lee. In addition, the signs often were placed so that drivers stopped for lights or traffic would look directly at them.

Cleveland's digital signs were along interstate highways and required drivers to look away from the roads to catch the messages. "From a driver's perspective, that was a worse situation," she said.

The test subjects were not told what the study was about. The digital billboards along the route changed messages every eight seconds and did so instantaneously without distracting special effects.

After studying the data, the researchers concluded, "Although there are measurable changes in driver performance in the presence of digital billboards, in many cases these differences are on par with those associated with everyday driving, such as the on-premises signs located at businesses." In other words, the boards were distracting but no more than many other things encountered during the drive.

The conclusion also suggested an analysis of accident data would be needed to understand the signs' impact. The second study the foundation commissioned examined that issue. Philadelphia firm Tantala Associates found accidents along the Cleveland route were no more likely to occur near digital billboards than on sections of the highway without them.

Neither study is credible, in Mr. Fry's opinion. He noted the Virginia Tech researchers had done a previous study on conventional billboards for the foundation that one judge cited as being influenced by the industry. Meanwhile, Dr. Lee defended her study and said the researchers took special precautions to avoid bias.