FORT LAUDERDALE, Fla. -- Digital billboards on highways are bright and constantly changing, but critics think they are a danger to drivers.

"They show up more, that's for sure," driver Sam McFarland told Local 10's Jen Herrera.

The signs are big and bold and they do exactly what they are supposed to do. Whether it's getting you to take a cruise, drive a certain car, or go somewhere to have fun, the billboards get your attention.

"I think they're pretty interesting," said Phillip Thompson. "They keep switching from one ad to the next."

The ads on the digital billboards -- up to six ads per sign -- change every six to seven seconds.

The signs are growing in popularity, but critics say they are a dangerous distraction.

“I usually read them when I'm at a stop light," Thompson said.

But other drivers said they could do without then.

"They kind of take you by surprise," said Renee Armas. "It's kind of distracting."

There are an estimated 450,000 billboards across the United States. About 2,000 of those are digitized.

Some safety advocates want them taken down. But as of now, there's little proof that they cause problems.

"At this time, we haven't worked any crashes where a driver has said that was a distraction," said Florida Highway Patrol Sgt. Mark Wysocky.

Meanwhile, the Federal Highway Administration is conducting a study to observe drivers and monitor their reactions as they approach the digital signs.

The results of the study are expected to be released in the summer.